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The streak may have ended two games earlier than Bayer Leverkusen might have hoped, Atalanta blowing to pieces hopes of an unbeaten season across all competitions, but a 51-match unbeaten run in all competitions remains a quite remarkable achievement for a club once defined by its inability to get their hands on silverware. Whatever the outcome of Saturday's DFB Pokal final against second tier Kaiserslautern, Xabi Alonso's will go down in history as the first undefeated Bundesliga champions. Win the German Cup too and they will be only the fifth side to win the double in Germany.

Not bad going for a side who came into this season with no one talking about them as champions in waiting, let alone a team that could set the longest unbeaten run by a European club in the era of UEFA competitions. This is the story of that run in 10 moments:

1. Xabi Alonso arrives (October 5, 2022)

Eight games into the 2022-23 Bundesliga season and Bayer Leverkusen were in crisis. A 4-0 loss to Bayern Munich had them 17th in an 18 team league. While some of that could be explained by misfortune in attack and good fortune for their opponents, it seemed a high risk juncture at which to appoint a head coach whose only previous experience was with the Real Sociedad B team. "People were not clapping when we hired him," said chief executive Fernando Carro. "People said he has no experience, why do you do this?"

It was not a given that Alonso would jump when the Leverkusen hierarchy came to San Sebastian. He had had opportunities in the past, turning down the Borussia Monchengladbach job because the feeling wasn't quite right. This time around he got it. "I had an idea that I didn't want to go too quick," he said in November 2023 of his fledgling managerial career. "After is a little bit of intuition, connection with the right moment in the right place.

"From the first moment I had the feeling that everyone was pushing from the same direction. That's really helpful. Even in the first couple of months the results were not the best, but I didn't have any kind of nerves." Results would pick up, culminating in a run to the Europa League semifinals and a league finish that meant they were back in the competition the following year. Even though their season ended in defeat, Leverkusen were on the right track.

2. Granit Xhaka signs (July 6, 2023)

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Alonso wanted more, and the man who had won all the biggest prizes that football had to offer -- who is adored at Liverpool, Real Madrid and Bayern Munich -- had a sense of what would be needed to push his new club up a level.

"His experience and proven success as a player makes everyone believe that he knows what a club needs to be successful," said Carro. "What he says make a lot of sense. It has an impact. When we discussed tranfers for the summer in St. Louis [during the winter break extended by the 2022 World Cup] he wanted to have a balanced team of experienced players."

That is what he was afforded in the summer of 2023. Jonas Hofmann, 31, arrived from Borussia Monchengladbach for €10 million. Alejandro Grimaldo, then 27, was picked up when his contract at Benfica expired. Then came a 30-year-old who had proven to be one of the most polarizing players in the past half decade of Premier League football. Leverkusen don't buy players like Granit Xhaka. Their recruitment model has tilted younger for several years, players who might need anywhere up to two years to establish themselves but whose value will increase over time. Moussa Diaby is the exemplar, his €55 million sale to Aston Villa largely funding a squad overhaul that included the veterans listed above but also younger talents such as Victor Boniface, Arthur and Nathan Tella.

For Xhaka, the lure of a five year contract was hard to turn down at a time when Arsenal were looking to upgrade the left eight position he had approached with such purpose in his final year. The Gunners, meanwhile, could hardly believe the price they got. Talks began for a deal at around €15 million but, sources say, it soon became apparent to sporting director Edu and director of football operations Richard Garlick that Leverkusen were laser set on the Swiss international. They pushed the terms up to €25 million, the third highest fee Leverkusen have ever paid.

It ultimately proved to be a price worth paying. Alonso views Xhaka as a connective force between the coaching staff and the dressing room, a man who could enforce standards across the club in a way he couldn't. As Carro put it, the new midfielder was "the key position in the game itself." Arguably no addition would have a more critical role than Xhaka, who led the Bundesliga in touches, passes and carries. More than that he returned to Germany with the steel of a man who had been pipped at the post by Manchester City several months earlier. He was determined that wouldn't happen again.

3. Bayern draw shows progress (September 15)

Three games into the Bundesliga season, it was Leverkusen who were the early pace setters. It would not have been wise to get carried away, an opening day win over RB Leipzig had been impressive, but neither Borussia Monchengladbach nor Darmstadt particularly promised to set the league alight. What would really test the early league leaders was a trip to Bayern Munich, the champions who looked so radically enhanced by Harry Kane's presence.

Early on it looked like Bayern were about to do to Leverkusen what they so often to do to the Bundesliga's plucky upstarts. The visitors didn't help themselves by handing two iron clad chances to Kane, the first a header he converted at the back post before Lukas Hradecky denied him acrobatically. Leverkusen kept coming at the other end, Victor Boniface a tyro that Min-Jae Kim and Dayot Upamecano could not keep from shooting positions. Alejandro Grimaldo go their first equalizer with an excellent free kick before the first in what would be the season's great rush of late goals.

Five minutes after Leon Goretzka had turned home Bayern's second, the video assistant referee spotted a shove on Hofmann just inside the penalty area. Up stepped Exequiel Palacios, in went the first post-90 minute goal of the campaign. Only another 14 to go.

4. Eintracht Frankfurt smoke Bayern (December 9)

As much as it is true that Bayer Leverkusen won the Bundesliga on their own steam, it certainly helped no end that the Bayern Munich side pursuing them became too frequently incapable of turning adequate performances into adequate results. This was a serious team whose underlying metrics suggested they should, at the very least, have made a real fist of defending their title. But where Leverkusen tended to deliver in the clutch, Bayern only ever seemed intent on making games harder for themselves.

The rot really set in for Thomas Tuchel's side, who before then had also unbeaten, with a 5-1 pummelling in Frankfurt. It was typical of how Bayern slipped out of contention that they should turn 20 shots and 2.1 xG of their own into one goal while allowing Eintracht Frankfurt to get five from 14 and 1.3. That last figure might have been even lower if not for the sort of basic mistakes that handed goals to their hosts: Noussair Mazraoui shanking a clearance under little pressure, Dayot Upamecano sucked towards the ball to give Hugo Larsson the space to strike a third. This would set the tone for the remainder of the season. Bayern always found a way to make it harder for themselves as Leverkusen would discover in the early spring.

5. AFCON tests squad depth (January 13, 20)

Top of the table at die winterpause, unbeaten in the Bundesliga with the title an extremely real prospect, Leverkusen's sporting director Simon Rolfes had been here before. It didn't go so well back in 2009-10 where Die Werkself collapsed down the straight to fourth place, not only missing out on a first title in their history, but even Champions League qualification. A prime piece of Neverkusen.

This time would be different. This Leverkusen could hold firm through the absentees that the football calendar had delivered on them. Odilon Kossounou, Edmond Tapsoba and Amine Adli departed for the Africa Cup of Nations. Boniface would have joined them. but he suffered a groin injury in the build up to the tournament. The 23-year-old would start only three more matches for Leverkusen before the DFB Pokal final. Still, Rolfes did not see a reason why the 2023-24 iteration would struggle like the one 14 years earlier.

"We have more quality now," he told CBS Sports. "What we had in that season, for example, we missed three important players for a long time. Patrick Helmes, our top striker, with a cruciate ligament nearly all of the season. Renato Augusto, a top player, and myself as well, I missed two-thirds of the season. At that time we were not able to change players so much, we didn't have such a good squad. We had 13, 14 players but then the level dropped. 

"This is the big difference to this season, that we have a squad of 18, 19 players who are competing for a starting XI position. They all have the expectation and ambition, how they see themselves, to be an important part of the team. This creates a dynamic. This creates competition."

A more settled XI had got Leverkusen to Christmas, but now Alonso would chop and change. In Augsburg a back three of utility defender Josip Stanisic, midfielder Robert Andrich and Piero Hincapie held out for a clean sheet in a 1-0 win where Florian Wirtz was also missing. The next week Hincapie struck at the death against RB Leipzig, a 2-1 deficit in the 56th minute becoming a 3-2 win. It was grit your teeth stuff from Leverkusen, drawing 0-0 against Borussia Monchengladbach, the last time they dropped points before they were crowned champions.

"We always said to focus on the next game, focus on a short term period," Rolfes said of the winter period. "We really did this, there were no discussions on can we win [the league] or not. Let's win more games. Then we had the Africa Cup of Nations, that was proof. We miss important players, we only have a small squad available. How will we react? We did it."

6. Alonso's tactical masterclass (February 10)

Underwhelming though Bayern were, that hadn't stopped them winning the title in recent years. As Borussia Dortmund could attest, Tuchel could lead Bayern to a title in spite of themselves. Had Munich won at the BayArena then they would have taken top spot in the Bundesliga and there was certainly enough to have you believe they might. Leverkusen had just been through a gruelling DFB Pokal quarterfinal with Stuttgart, won at the death by Jonathan Tah's headed goal. Bayern had had a free week and were boosted in the run up to the game by the revelation that Joshua Kimmich would be free enough to play some part in a game where victory would have propelled them into top spot.

They never got close to that win. As had been speculated in the lead up to the match, Tuchel had opted to mirror Leverkusen's 3-4-2-1 with new signing Sacha Boey handed the left flank, a tough task for a right back new to the Bundesliga. Alonso seemed to have seen the move coming, responding to Bayern's gambit with a feint of his own. Jeremie Frimpong was only fit enough for the bench after knee issues but it was Stanisic, on loan from the champions, who got the start rather than the more like for like Nathan Tella. 

The Croatian's presence allowed Leverkusen to form a true back five, Boey was challenged to progress the ball up field and Bayern fell apart in possession. They never got together off the ball and there was no little irony in Stanisic being the one to spoil the title hopes of his team mates with a back post finish. Grimaldo and Frimpong netted in the second and Leverkusen were five points clear. This was the moment when they knew they had to bury the ghosts of those early 2000s sides and the trophies they didn't win.

"For sure there was a moment where you said this season, how we play, our results, now we have to show it," said Rolfes. "We have to do it. It's not an option to fail, it's not possible. We have no possibilities but to win the Bundesliga title."

7. Alonso says he's staying (March 29)

The title might have been a forgone conclusion by the time spring arrived, but how long this Leverkusen side might stick together was a more open question. It is a familiar tale over recent years, a breakthrough side on the European stage is swarmed upon by the Premier League and Europe's richest clubs. Before they even get a chance to fulfil their collective potential, burgeoning talents are cast to the winds.

Leverkusen didn't just have that question hovering over them, but another about the manager. Alonso was a hugely admired figure at Liverpool and Bayern Munich and both of those were about to have vacancies. The latter, in fact, seemed to announce Tuchel's summer departure with a view to beating the Reds in the race for the man who was working wonders at the BayArena.

Long before Jurgen Klopp announced he was leaving Anfield, the Leverkusen hierarchy had been facing questions over Alonso's future. They had been publicly and privately relaxed, reasoning that if their head coach was really in demand, it would probably be because their club were enjoying great success. Alonso, for his part, had seemed utterly at ease with the speculation over his future. However, as Rolfes acknowledged, when it is Bayern and Liverpool on the hunt, jitters are only natural.

"My feeling was always that he would stay, that he appreciated a lot what he has here, maybe also with his family life here and how we work together," said Rolfes. "For sure that's a feeling but you never know for sure."

During the international break in late March, Rolfes, Carro and Alonso sat down for talks to settle the matter once and for all. The head coach was fully abreast of Leverkusen's recruitment plans for the summer. He did not seek any further assurances before making his commitment. He would stay, announcing as much in his pre-match press conference before a game against Hoffenheim. That perhaps the most highly regarded young manager in the sport wanted to stay where he was proved to be rocket fuel for the run in.

"This decision he made in a positive way had also a positive impact for this season," Rolfes adds. "The head coach believed in us and our future success this season and next. This helps. For sure the other way around would have been challenging.

"He knows what we can get and what is possible. He knows we are ambitious as a club as well to develop and to keep this level, to maybe change the squad in a way that we have a competitive team next season, to refresh the team and create a new dynamic."

8. Champions (April 14)

With five games still to play after, the title was won with a flourish in mid-April, Werder Bremen the unlucky ones to turn up at the BayArena when Leverkusen could do the business. Florian Wirtz's second half hat trick put the gloss on a 5-0 win that was greeted with fans streaming onto the pitch. For so much of their 120 year history Leverkusen -- UEFA Cup winners in 1988, German Cup winners five years later -- had been defined as much by the teams that hadn't won, most famously the 2002 vintage led by Michael Ballack, a man who took just about every second place going that year.

Within minutes of the final whistle you could only see one or two patches of green as the BayArena pitch became a sea of red and black, hundreds grabbing at players to thank them for the most remarkable of seasons. It wasn't quite over just yet.

9. Are they really going to do it? (May 9)

Even with the title won and talk of the unbeaten season building, the odds were still against Bayer Leverkusen. Even the most outmatched of opponents that the German champions could face might have a 10 percent chance of winning a game. Most had much better odds, particularly as the final rounds of the Europa League threw up more challenging fixtures. Stanisic's 98th minute equalizer against Borussia Dortmund hinted that this side wouldn't settle just for silverware. "We played with such ambition," said Rolfes.

That ambition was plain to see in their run to the Europa League final. Against Qarabag they were pulling a never-ending stream of magical goals out of their sleeves, West Ham were undone in the closing stages of both quarterfinal games. Then there was Roma. It should have been easy street for Die Werkself, two goals to the good from their trip to the Italian capital. The ball, however, wouldn't go in for them early on. Two penalties and it wasn't just the unbeaten run on the line, they might be going out of the competition altogether. 

A Gianluca Mancini equaliser at least put Leverkusen on the road to Dublin but still they pressed, relentlessly pursuing their place in the history books. They might have played down the record over the trophy when they were beaten in the final but those players in black and red that night clearly would not settle for a qualifying defeat, not when they were on the cusp of breaking Benfica's 59 year old record for the most games undefeated in European football history. "To come back against a team with so much experience and, above all, not to lose is incredible," said Xhaka. "Once again, this determination to score another goal and go for it again is unbelievable."

Not for the first time this season, Stanisic was the hero. It had been Patrik Schick who saved the streak against Qarabag, Andrich at home to Stuttgart, Adli at Hoffenheim. Squad player or superstar, everyone was delivering when Alonso entrusted them.

"That was a really important thing, that everybody tried to push the dynamic of the team if you're playing or not playing," said Rolfes. "At the beginning of the season we had seven times in a row the same starting XI in the Bundesliga but this changed through injuries, through the games. 

"Now we have the situation that Xabi is changing, more or less always, six, seven, eight players in important matches. It's not like this player is playing important matches and the other isn't. Everybody is involved. Everybody is committed to the team and plays an important role for success."

10. An abrupt end (May 22)

It was then a bitter irony that Alonso's faith in the changes he had made over the course of the season backfired in the Europa League final. Boniface had had few minutes afforded to him since returning from injury and Adli took his place for the XI. Stanisic's reward for an excellent season was the right wing back berth, Frimpong moved further up the field and into the front three at Hofmann's expense. The changes never quite worked. Atalanta's aggressive press challenged Leverkusen to go long but when they did, typified in the second goal in Ademola Lookman's hat trick, the ball came straight back towards them from a front three that couldn't hold possession.

"Maybe something wasn't right," Alonso acknowledged after the game. "There were a lot of one-on-one situations. Maybe we made too many small passes in the last phase. Today, we should have played a few long balls."

Still it speaks volumes of what Leverkusen have achieved this season that no one would write their obituaries at half time of a game where the tactics weren't working, the players were losing individual battles and Atalanta had a two goal deficit. That, more than the unbeaten season they did not quite manage to have, really ought to be what defines the 2023-24 season.A team without superstar names, 19 months out of the Bundesliga relegation zone, have developed an aura of invincibility. In the process they have done what no Leverkusen side every did before, something they themselves might not have dreamed of at the start of the year, winning the Bundesliga. Come Saturday night there is a strong chance their trophy cabinet will have doubled in size.

The story need not even end against Kaiserslautern on Saturday. Alonso has committed to a crack at the Champions League and so has Wirtz. Leverkusen may choose to sell from their fringes but they are certain they will keep hold of their core, at least for the time being. These players may have more history to make.