Schafer threw to the wrong base on a sacrifice fly in the second inning, throwing to third base when he didn't have a realistic shot of getting the runner. Meanwhile, Pedro Alvarez advanced from first to second base and eventually scored.
"I just felt that play and behavior didn't match what we needed to get done and what everybody was doing," Mills said. "We came out of the gate busting our tails, guys were going first to third, first to third, and putting ourselves in position to score a lot of runs. His behavior didn't match what we needed to have done."
Mills didn't elaborate on any other issues he had with Schafer. Earlier in the inning, though, Garrett Jones hit a blooper in front of Schafer and was able to race into second base for a hustling double.
Schafer, acquired a year ago from the Braves as part of the Michael Bourn trade, is hitting .236 with three homers, 20 RBIs and 19 stolen bases for the Astros. He admitted he should have thrown the ball to second base.
"Yeah, he was right," Schafer said. "It was a slow runner and the ball was hit deeper than I thought and I should have threw the ball to second base."
When asked about the other play, Schafer said: "I'm really not going to comment on the other play. We saw things a little bit differently. He's the manager and he did what he thought was right and I have no problem with it. I 100 percent should have thrown the ball to second base and that's my fault."
Schafer was asked if he thought there would be a problem going forward.
"I need to go out and play hard and whatever happens, happens," he said.