[CBeisbol]

People were asking about coaches, so I decided to take a quick look

OOTP XX - Standard Game

All league settings set to discourage randomness (no trades, no development, no injuries, personalities and morale off, etc)

Phillies as the test team

Altered the ratings of the pitching coach and hitting coach
Base: all ratings = 100
Good: all ratings = 150
Bad: all ratings = 50

16200 (10 seasons) game sims for each test


RESULTS:
No obvious effect
With the pitching coach, the team won more games with the good coach and the bad coach. They gave up less runs with the good coach and the bad coach. ERA was .01 better with the good coach, but equal with the bad coach. Walks were the same with the good coach, but better with the bad coach. Fewer strike outs with the good coach, and even fewer with the bad coach.

With the batting coach, the teams also won more games with both the good coach and the bad coach. But the team scored almost 10 more runs with the good coach, while scoring 3 less with the bad coach. Batting average was .001 better with both coaches. Walks were slightly higher (.01) with the good coach and slightly lower (.01) with the bad coach. Strikeouts were down with the good coach, but down more with the bad coach.



EDIT
As pointed out in the following posts, but not made clear in this post, this study gives evidence that coaches have no direct impact on performance

Coaches would still be expected to have an indirect impact on performance through development and morale.