It hasn't been pretty, and it certainly hasn't been easy, but the Houston Astros have reasserted themselves as a legitimate threat in the American League thanks to a five-game winning streak. The Astros, who will open a brief series on Tuesday against the Colorado Rockies, are now just four games out of a wild-card spot and six back of the Seattle Mariners in the American League West. They're coming off a weekend sweep over the Orioles that saw them outscore Baltimore by a 27-13 margin in a series that featured Corbin Burnes and Grayson Rodriguez starts. 

Make no mistake, the Astros continue to be plagued by pitcher injuries. Justin Verlander is back on the IL with neck discomfort, once again giving Houston a formidable rotation of ailing pitchers -- a group that also includes the likes of Luis Garcia, Cristian Javier, Lance McCullers Jr., and José Urquidy. Even the injury replacements, like rookie Jake Bloss, have gotten hurt. (Star outfielder Kyle Tucker is also on the IL, nursing a shin contusion that has sidelined him since early June.)

Nevertheless, the Astros have atoned for a miserable 10-19 opening stretch by going 28-21 since the start of May. How have they done it? Let's take a look at three factors driving Houston's resurgence.

1. Stars aligning

We don't mean this in the "they've gotten lucky" sense; we mean this in the "their best players have simultaneously heated up" sense. When you think of the Astros, you probably think of Jose Altuve, Alex Bregman, and Yordan Alvarez. Coincidentally, those three have been the driving forces in the lineup as of late. Take a look at how each has performed in the past 30 days:

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BatterBAOBPSLGwRC+

Altuve

.300

.336

.436

121

Alvarez

.326

.387

.632

182

Bregman

.343

.395

.571

175

If you're unfamiliar with the wRC+ metric, it's a catch-all measure housed at FanGraphs that controls for ballpark and other factors. For further context, consider that Mike Trout's career wRC+ is 169. The Astros, then, have had two players -- Alvarez and Bregman -- performing better than average Mike Trout for the last four weeks. Altuve's 121 mark is nothing to scoff at, either; his career mark is 130, suggesting that he's the rare 34-year-old second baseman who hasn't lost a step.

It's a good thing those three have been hot at the same time, too: Yainer Diaz and Trey Cabbage are the only other Astros batters with at least 30 plate appearances and a wRC+ over 100 in the last month. Even so, the excellence of Houston's top three has resulted in an offense that ranks 13th in runs scored -- while that's not a great mark by itself, it's impressive given the lineup's context.

2. Run prevention unit stepping up

Remember all those Astros pitching injuries we noted in the introduction? They haven't stopped the Astros from posting the fifth-best ERA in baseball over the last 30 days.

Framber Valdez and Ronel Blanco, the author of MLB's only no-hitter this season, have continued to be excellent at the top of the rotation; the bullpen has rounded into a better shape -- at least with respect to Bryan Abreu, Seth Martinez, Tayler Scott, and Josh Hader; and we'd be remiss to omit Hunter Brown, who has recovered from a miserable start to the year by compiling a 1.45 ERA and a 27.7% strikeout-minus-walk percentage over his last five outings. (For reference, that would be the fourth-best mark in MLB, between Tyler Glasnow and Chris Sale, if Brown had managed it all year.)

Credit this statistic in part to those pitchers and in part to the talented fielders they have -- including Bregman, Jake Meyers, and Jeremy Peña -- but the Asros have third-lowest batting average on balls in play over the last month. The Astros do hand out their share of free passes, yet they've done a nice job of preventing those baserunners from becoming runs. 

We suspect that the Astros will be aggressive in improving their pitching depth between now and the July 30 trade deadline. Houston should have internal reinforcements coming, too, provided that Verlander, Garcia, and McCullers are able to rejoin the staff over the next month-plus.

3. Rivals slipping

The Astros' reemergence in the playoff picture cannot be attributed only to their improved play; we feel obligated to note that they've benefitted from some down stretches by their rivals.

Coming into May, the Astros had the second-worst record in the American League. They've since posted the fourth-best record in the AL, winning more than 57% of their contests. (That's a 92-plus win pace over 162 games.) All the while, the Astros have gained some serious ground on the rest of the pack, leaving them as the second-best team outside of the tournament. 

How's how their top AL competition for a playoff spot have fared over that same time:

TeamAstros GB on May 1Win% since May 1

Yankees

8

67.3%

Guardians

9

65.2%

Orioles

9

62.5%

Mariners

6.5

56%

Twins

6

55.1%

Red Sox

6.5

52.1%

Rays

3

51.1%

Royals

7

50%

Rangers

5.5

44.7%

Blue Jays

4

43.5%

Tigers

6.5

40.4%

As you can see, three teams have posted a losing record, including the defending champion Texas Rangers; a few other teams have played around .500 ball, give or take; and then you have the likes of the New York Yankees, Cleveland Guardians, Seattle Mariners, and Minnesota Twins, each of whom have played near or above a 90-win pace themselves.

How have the Astros been able to reinsert themselves into the playoff picture? In the simplest terms, by outperforming most of the American League for close to two months now.