Before the game, Weiss said Fowler injured his lateral collateral ligament (LCL) when he tried to steal second in the first inning of Monday's 6-1 win over San Francisco.
Asked if the Rockies center fielder might return for the series against the Reds that begins Friday, Weiss was cautiously optimistic.
"It would probably be a stretch to see him out there on Friday," Weiss said. "But maybe at some point during the weekend."
After opening the season on a tear, Fowler's bat has cooled. He's batting .263 with 12 homers and 42 RBIs in 110 games. Charlie Blackmon started in center field and hit leadoff on Wednesday.
Ian McCue is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.