Gennett underwent an MRI to determine the nature of his injury after he left Friday’s spring training game against the Milwaukee Brewers.
Gennett ranged to his left for a ball off the bat of Yasmani Grandal leading off the second inning Friday. Gennett slid to make the stop and threw to pitcher Robert Stephenson covering first for the out. Gennett went to his knees and was helped off by Reds head athletic trainer Steve Baumann and manager David Bell.
The 28-year-old Gennett reached the majors with the Brewers in 2013 and was claimed off waivers by his hometown Reds near the end of spring training two years ago. He made his first All-Star team last season, hitting .310 with 23 homers and 92 RBIs.
Top prospect Nick Senzel also could be a candidate to replace Gennett. Senzel was reassigned to minor league camp earlier Friday.
The Associated Press contributed to this report.