After a 2020 season that was unlike any we had experienced in our lifetime, college football's return in 2021 felt bigger than usual. The combination of playoff expansion, NIL and conference realignment kept the conversation going all through the summer. When games were finally on the horizon, the return of fans in the stands brought a heightened, palpable excitement. 

Now at the midseason point, it's great to report that college football has indeed delivered on the promise of a season for the ages. The 2021 CBS Sports Midseason All-America team has highlighted some incredible individuals. Our second-chance picks for the College Football Playoff, Heisman Trophy and other national honors mirror the results of a chaotic first half that included 47 games lost by ranked teams.

Now, it's time to turn our attention to how the second chapter for the 2021 season will conclude. Below, we've detailed seven storylines to watch over the second half of the 2021 season: 

Georgia's claim as one of the best defenses ever

The conversation has already started. While comparisons across eras can get a little sloppy, every additional game the Bulldogs play seems to add to the argument that this unit is one of the all-time greats. 

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The strength of the argument is that evidence comes from all sides. Do you prefer to keep it simple, judging defenses by the impact on the scoreboard? If so, no defense since Alabama's in 2011 has held opponents under 10 points per game, That unit allowed 8.2 points per game and this year's Bulldogs are allowing a mere 6.6. If that's too basic for your tastes, the advanced efficiency metrics indicate that, at this pace, Georgia will have some of the best numbers since they started keeping such statistics. 

How about judging elite college defenses by the future NFL talent assembled in one place? While it may not take the crown from 2001 Miami, there will be Sunday afternoons in the future when we marvel that coach Kirby Smart had both Jordan Davis and Jalen Carter as his top two nose tackles, with defensive tackle Devonte Wyatt and linebackers Nakobe Dean and Nolan Smith all causing havoc as well. 

There are two hurdles left to determine Georgia's place among the all-time greats: how it performs against a top-tier quarterback and whether it wins its first national championship in more than 40 years. The best passing attack left on the regular-season schedule may be against Tennessee on Nov. 13, but that will only be the appetizer. More potent passing attacks surely await the Dawgs in the postseason, both in the SEC Championship Game and, in all likelihood, the playoff. 

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Alabama's position on Dec. 4

Nick Saban said this week that the identity of the 2021 Alabama team has yet to be decided. It's a group that has exemplified the kind of talent-forward dominance we're used to seeing from the Crimson Tide in spurts, but also some of the lags and lulls that drive the greatest of all time to rip off his headset and turn every shade of red. 

Penciling in Alabama as the No. 1 team in the nation was not unfair coming into the season, but the assumption that this team would be a continuation of 2020's dominance was misguided. New faces on the field and sideline signaled one of the most significant overhauls of the Saban era. Ultimately, it has left a margin for error much smaller than we're used to seeing. 

Florida first exposed that margin in an early-season scare in Gainesville before Texas A&M seized the opportunity, upsetting the top-ranked Tide 41-38 in the biggest win yet during the Jimbo Fisher era. Alabama still sits in first place in the SEC West and controls its divisional future, but what we will learn about the team's identity over the second half of the season? And what kind of form will the Crimson Tide carry into a potential SEC title game meeting with Georgia? If the loss to the Aggies was the wake-up call that leads to more consistent and efficient performance on the field, then Alabama's best football might be in its future. 

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Who emerges from the Big Ten East? 

Congratulations to the Big Ten league office for a conference schedule that is going captivate the college football world in the weeks ahead. The division has four teams in the top 10 of the AP poll — No. 5 Ohio State, No. 6 Michigan, No. 7 Penn State and No. 9 Michigan State — with a combined record of 23-2. All four are going to play each other over the second half of the season. 

The divisional title chase starts with a bang on Oct. 30 as Michigan plays Michigan State and Penn State travels to Ohio State. The odds favor Ohio State emerging as the Big Ten's champion and top playoff contender, and the leaps taken by a healthier, more experienced CJ Stroud back up that suggestion. However, 2021 is as tough as the division has been in years. Coach Ryan Day's undefeated record against conference teams is going to get its toughest test yet. 

Beyond the Buckeyes, there are even more fascinating storylines. Michigan will try once again to beat Ohio State for the first time under coach Jim Harbaugh. Penn State and Michigan State are enjoying successes with in-demand coaches who are being named as potential candidates for other jobs. The Cover 3 Podcast recently ran a SEC West vs. Big Ten East head-to-head challenge akin to the ones we see in college basketball. While the SEC West won that debate, the top four of the Big Ten East provides enough juice to make it the most interesting division in college football. 

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Caleb Williams continues late Heisman Trophy run 

Oklahoma's freshman quarterback has just one career start as we enter Week 8. Still, Williams has been impressive enough to rocket up to fourth in the Heisman Trophy odds behind Alabama quarterback Bryce Young, Ole Miss quarterback Matt Corral and Ohio State quarterback CJ Stroud. While the national storyline will be centered around his argument as a Heisman contender in spite of his small sample size, Williams' story is among the most significant because of his importance to Oklahoma's national championship contention. 

One of the big storylines coming into the season was that Oklahoma was poised not just to make the field fo four, but pick up the program's first playoff win. That conversation was sparked from the presence of QB Spencer Rattler, the preseason Heisman favorite. But when Williams took over for Rattler against Texas, the story of Oklahoma's season changed dramatically. If the Sooners make a run at the title, the theater of what's transpired in Norman might be enough to grab the attention of voters looking to fill out those three spots on their ballot for college football's most outstanding player.   

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Cincinnati's high-wire act reaches its climax

The Bearcats beat Indiana and Notre Dame in consecutive games to set up one of the most intriguing conundrums of the playoff era. Now up to No. 2 in the AP Top 25 and No. 3 in the Coaches Poll, it stands to reason that the Bearcats are as well-positioned as any Group of Five team could be to finish the season in the top four of the playoff committee's rankings. To do so would be historic and shatter the perception that the door is closed to those outside the power conferences, no matter how the season goes. 

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Cincinnati was an undefeated conference champion when the selection committee revealed its final rankings in 2020, sandwiched at No. 8 between a three-loss SEC runner-up Florida and a two-loss Georgia. The Bearcats never made it higher than No. 7 that year, but if they continue this run, it's going to be awfully tough for the committee to put them outside of the top four. 

While there are aspects of Cincinnati's playoff push that are well outside of the program's control, like whether SMU is ranked when they play in November, it has a say in its own results. As the pressure mounts for making playoff history, each week will become a high-wire act to make it to the end of 60 minutes with another win. Based on where Cincinnati ranks now and what's already been accomplished, the most important stat for national championship contention is not margin of victory or strength of schedule, but that "0" in the loss column.   

Clemson tries to keep at least one streak alive

With the playoff out of reach, Dabo Swinney and this Tigers program have refocused on their goals of winning a seventh straight ACC championship. Florida State holds the league record with nine straight conference crowns from 1992-2000, but two of those titles were shared since they occurred before the championship game era. 

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The toughest part of winning another ACC title might be making it to the ACC Championship Game. The Tigers have a loss to a divisional foe in NC State, and the Wolfpack currently have the inside path to winning the division if they win out. Undefeated Wake Forest could also be a road block heading into the second half of the season. In the immediate future, Clemson's ACC title hopes will be on the line as the Tigers head to Pittsburgh as underdogs against the Panthers. 

High-profile coaching carousel swings

USC, LSU and Washington State already have vacancies that will be coveted by other coaches in the profession, likely sparking a busy coaching carousel for the headline-worthy programs. Additionally, several other Power Five programs with coaches on the hot seat will have to make tough decisions based on the results over the second half of the season. It might not be a typical coaching carousel of sheer volume, but it's going to be one with the potential to alter the landscape because of the blue-blood schools already involved and ones that could be in the hiring business soon.