Yelich was replaced by Ben Gamel in right field to begin the bottom of the fifth inning.
He singled in the fourth inning and was retired on Jesus Aguilar's double play. Brewers manager Craig Counsell said after the Brewers' loss that Yelich felt his back grab on him after he stopped on an attempted steal after his single.
"He's a little sore right now," said Counsell, who described Yelich as day-to-day.
Counsell said he will try to give Yelich a day off on Monday when the Brewers host the Rockies.
Yelich also dealt with back issues last season.
He hit his major-league-leading 14th homer in an 8-6 win over the Mets on Saturday. That tied him with Albert Pujols (2006) and Alex Rodriguez (2007) for the most through the first full month of the season.
The Associated Press contributed to this report.