Michaels was getting occasional starts against left-handers, but the Astros might only face two or three southpaws the rest of the season.
The absence of Michaels, who underwent surgery on Wednesday to repair a broken bone in his left hand, could mean a few more at-bats for rookie J.B. Shuck, who had three hits off the bench in Tuesday's win over the Phillies.
Michaels' injury capped what was a frustrating season for the outfielder, who batted .199 with two homers and 10 RBIs in a part-time role. He was 8-for-45 (.178) as a pinch-hitter.
"He's a good guy to have on the ballclub," manager Brad Mills said. "He's going to have give you the best at-bat he possibly can each time out as a veteran guy. You can't underscore that significant influence he has."
Michaels, of course, never lost his sense of humor after coming out of the game Tuesday when he wasn't able to close his glove or grip a bat.
"He said, 'I'm going to use this to blame my year,'" Mills said. "He's been around long enough to realize how he needs to look at things."