Dexter Fowler and the reason the Astros have played better

My intention in writing this article was to prove that the recent uptick in Houston's record, that has seen the Astros go 11-9 in its last 20 games, was due to Dexter Fowler's return. My point was going be that Fowler, who's hitting .306/.412/.458 has been an integral part of the offense over that stretch and one of the biggest reasons Houston's offense has rebounded.

I wanted to write that. I tried to make the numbers fit that narrative.

Turns out, Fowler's return only bolstered an already improved offense. Turns out, the biggest change for the Astros in the second half hasn't been runs scored, but runs allowed.

Let's talk a little about trends. Houston has scored 554 runs this season and 186 in the second half alone. That gives the Astros the second-biggest improvement in run differential in the majors to this point.

Biggest improvement so far in run differential over 2013: Mariners +223, Astros +152, Twins +131, Giants +122, Angels +114, Marlins +106.

— Mike Fast (@fastballs) September 4, 2014

Meanwhile, the Astros have allowed 643 runs this season and just 187 in the second half. On a per-game basis, that means Houston has given up 4.6 runs per game this year, but that number drops to 4.3 runs per game in the second half. The reason Houston has played like a .500 team since the All-Star break is because they have been. Though their record is still three games under .500 in the second half, the Astros' run differential says they should be just a tick below .500.

By month, Houston has allowed 5.1 runs, 3.8 runs, 4.5 runs, 6.0 runs and 4.0 runs per game. Cut out that awful April and the season number for runs allowed drops to 4.5 runs per game. That's not a ton of runs lost, though it's still higher than the 4.3 runs per game Houston's given up since the All-Star Break.

What changed?

It's hard to say. One of the biggest difference-makers defensively has been Jake Marisnick. Since the former Marlins and Blue Jays prospect came to Houston, he's been great defensively (by the measures we have). Defensive Runs Saved loves him, saying he's been worth 12 runs above average this season alone. Ultimate Zone Rating also loves him, saying he's been worth 6.6 Defensive Runs  in the last 30 days thanks to excellent range.

Over the last 30 days, Marisnick has been the third-most valuable Astro, according to WAR. We've talked all summer about the problems inherent in using small samples for Wins Above Replacement, but considering Marisnick and Jason Castro are the only two Astros with positive defensive ratings in that period...you know what? Let's just forget this point. It's too hard to suss out what impact defense has in less than a full season.

We do know the offense has gotten substantially better than it was early in the season. Houston scored over 120 runs last month, the second time that's happened this season. Since that awful April, where the Astros only managed 88 runs, they've scored runs at a clip of 4.2 per game. Since Fowler returned from the disabled list on August 13, Houston has scored 4.4 runs per game, slightly above the 4.3 runs per game they've scored in the second half.

How has the offense remained consistent, despite losing guys from time to time? Looking back on the season, it's easy to explain. The post-April surge can be attributed to George Springer and Dexter Fowler rounding into form. Jose Altuve has remained a constant. When Springer and Fowler went down, Chris Carter went crazy and has remained hot the entire time.

Before the All-Star Break, Houston had three good hitters in the lineup with Altuve, Springer and Fowler. Now, Houston also has three good hitters in Altuve, Fowler and Carter. Fowler's return gives Houston a spark, but it's really been the improvement in run prevention that has caused the Astros to turn the corner lately.

Could that be Marisnick's defense? Could it be replacing Villar's defense at shortstop? Could it be Castro's defense behind the plate? Could it be Brad Peacock settling down, Collin McHugh and Dallas Keuchel bouncing back from July bumps in the road? Could it be that Marisnick's addition has cancelled out the loss of Jarred Cosart?

I started this article trying to prove the impact that Dexter Fowler has had on the team since returning. I finish it with more questions than answers. Seems about right for this team, which has struggled off the field but gotten better on it.