"We're kind of monitoring him a little bit," Mills said. "After he played in the doubleheader [Monday in Denver], he doesn't really know how he hurt it, but it was really bothering him and was extremely sore. We really need to try to stay away from him."
Buck was in the on-deck circle as a possible pinch-hitter in the sixth inning Thursday, but he didn't get into the game. He leads the Major Leagues with a .538 batting average as a pinch-hitter this season, which is his first in the National League.
"We're going to monitor him the next couple of days and see where we are," Mills said.