All Star second baseman Rickie Weeks appears headed for the disabled list after injuring his left ankle during Milwaukee's 2-0 victory over the Chicago Cubs on Wednesday.
The Brewers infielder appeared to turn the ankle while running to first base in the second inning and was unable to put any weight on it when helped off the field.
Weeks was taken to a hospital for further evaluation after initial X-rays found no broken bones.
Batting .272 with 19 home runs, Weeks is a major figure in the lineup for the National League Central-leading Brewers (56-49) and his absence would be a major blow.
"Rickie is an enormously productive player, a legitimate leadoff or No. 5 hitter with a huge amount of production," Brewers principal owner Mark Attanasio told the team's website (Milwaukee.brewers.mlb.com).
"That's not replaceable ... We just hope he's not out for a long time."