The Astros’ closers (Hawkins, Valverde) are flyball pitchers and Carlos Lee is one of the worst flyball catchers around. But Michaels doesn’t make a lot of sense in that situation. Michaels doesn’t appear to be appreciably better than Lee, defensively. And he has made a couple of gaffes in LF. The defensive replacement needs to be much better than Lee to make any sense. Given the current roster, Erstad is a better choice as a defensive replacement than Michaels. Of course, we need better hitters as outfield back ups, but that is a more general problem with the bench.

Also, I’m not sure that I would put a defensive replacement in the game with only a 1 run lead. A more traditional approach would be to use a defensive replacement with a 2 or more run lead. But that is kind of a subjective call, since you are trying to balance the need for better defense in LF with the risk that you have a tie game or worse after the top of the 9th. Maybe Cooper should give more consideration to the liklihood that Lee will come up to bat in the bottom of the 9th.

To some degree, I think Cooper gets caught up in the desire to make double switches in the 7th and 8th inning, and that drives his decision more than defense.

if he can’t play 9 innings then he should be in the American League

Yes, he probably should be in the AL, playing primarily as a DH.

But, he isn’t. And the Astros have to make do the best they can in balancing his offensive ability vs. his lack of range in the outfield. Cooper may not be the best at making those decisions. But almost every outfielder with similar profile (good offense / bad defense) is replaced in certain late game situations for defensive purposes. This is standard managerial practice.