The Reds also announced Thursday that right-handed starter Jeff Hoffman has been put on the 10-day injured list with a sore shoulder.
Senzel, who began the season as the center fielder before moving to third base, has been on the 10-day IL with left knee inflammation since Friday. He hasn't played since May 17.
Senzel and Hoffman are the latest injuries for the Reds. First baseman Joey Votto is recovering from a fractured thumb. Mike Moustakas, who moved from third base to first base after Votto was hurt, is out with a heel injury.
Outfielder Aristides Aquino, on the injured list since April 16 when he had hand surgery, is expected to begin a rehab assignment at Triple-A Louisville in the next week.