"He's improved today," Brewers manager Craig Counsell said Wednesday, ahead of an 11-9 win over the Reds. "We'll go through a bunch of treatments today and see how he is. The day off [Thursday] factors into all this. We'll see what we've got on Friday."
Yelich leads the major leagues with 19 home runs and is batting .325 with 41 RBIs in 44 games, including 42 starts.
He missed parts of seven games this season because of back problems and also missed time last season.
"I don't think chronic is the right word," Counsell said. "His back is an issue, but this isn't a structural issue. He's had some muscle issues in his back, but they've been short-term injuries. That's not a chronic characterization, for me.
"It's something that he's going to have to actively manage. These are small little things that are costing him a day here and a day there. Not worrisome from my end."
Hernan Perez replaced Yelich in right field and went 3-for-5 with a double and an RBI.