Why Are the Astros Winning? They Have Lots of Good Players

How do you build a good baseball team?  It's different than in the other two major American sports. In basketball, it is essential to have a star--an Hakeem or a Giannis--and surround him with another star or two and a bunch of complimentary players who know their role. In football, the key is the quarterback. For years, the AFC Championship seemed to be a battle between Tom Brady's team and Peyton Manning's.  Now it goes to Pat Mahomes's son's team, who faced off against Brady in the last Super Bowl. . 

But baseball does not revolve around stars in the way that these other sports do. As fans of an AL West team, we are well aware of this. At the end of this season, the Angels will have won more MVP awards over the last decade than they have played playoff games. Shohei Ohtani is awesome, and Mike Trout is even more awesome, but these superstars have not been able to overcome the dreck the keeps occupying the rest of the Angels roster.

The Astros contrast to the Angels. They Astros may lack a clear MVP candidate this year--Carlos Correa and Kyle Tucker will both win down ballot votes, but won't come close to the honor--but they are on the brink of claiming a more valuable prize--the AL West crown. And they are going to win their fourth AL West title in five years through the formula of having more good players on their team than their competition within the division. 

One way to show how the depth of the Astros roster is by noticing how many players the Astros have who are above the league average on offense. Of the 23 position players who have batted for the Astros this season, 13 of them have an OPS+ of 100 or greater. OPS+ is a stat which takes OPS, normalizes for park factors, and then puts it on a scale where 100 is exactly league average. Larger numbers are better. 

So the Astros have a majority of players with an OPS+ plus greater than 100, but an even greater share of their plate appearances go to these players. Of the 5,941 plate appearances that the Astros have this season, only 1,348 have gone to players who have an OPS+ of less than league average. 

That is a lot. In the figure below, you can see that the Astros have given 77.3% of their plate appearances this season to above average hitters. That's second best in the majors, behind only the Rays (who similarly have a lot of good players but no superstar). 

And while this is chart is a blunt instrument (guys at 101 OPS+ make it, while those at 99 don't; and there's no credit for having guys at 120 rather than 110 or 90 rather than 80), you can see that it is a decent proxy for success. The top teams on the list (Rays, Astros, Red Sox, Giants) are all headed to the playoffs. The bottom teams (Indians, Pirates, Rangers, Rockies) are not. 

I also highlighted the Angels, who have given only 32.3% of their plate appearances to batters who are above average. The Angels have the best player in the majors this season in Shohei Ohtani, but they have been hurt by their inability to find average to above average players to build depth beyond they core of superstars. Even if injured superstars Mike Trout and Anthony Rendon had been able to give the Angels 600 PAs this season, they would have had difficulty making up for all of the David Fletcher (OPS+ of 74) and Phil Gosselin (OPS+ of 90) plate appearances.
Who have received the 22.7% of Astros plate appearances that have gone to players who are below average hitters?  All three catchers who have played for the Astros this year have OPS+'s below 100 (Madonado 62 OPS+ is; Castro 96 OPS+ s; Stubbs 26 OPS+ ). They have gone to Quad-A guys who were up to provide depth (Robel Garcia, Jacob Wilson, & Taylor Jones). And they went to Myles Straw, who had a 85 OPS+ in 370 PAs for the Astros before his trade to Cleveland. 
Straw's plate appearances went instead to the rookie combination of Chas McCormick (107 OPS+), Jake Meyers (103 OPS+),  and Jose Siri (168 OPS+). This helps show why the Astros have so many above average hitters. They have been able to develop young players to take over from older ones and match or improve on their performance. They have done this at DH, where Yordan Alvarez has improved on the efforts of Evan Gattis and Tyler White. They have done this in right field, where Kyle Tucker is an upgrade on Josh Reddick.  In center field, they have not replaced George Springer's production. But in 2021, the Astros have identified their best options to play in centerfield and will have better options in centerfield than if they had stuck with Straw. 
Depth leads to success. It is essential to a have lots of good player to win in baseball, and the Astros continue to develop and identify good players.