Detroit said Martinez has left knee inflammation. He had surgery on that knee in February after tearing the medial meniscus.
"We had a plan back in April. It hasn't worked out," Detroit manager Brad Ausmus said. "He had a cortisone shot last Thursday, and we gave him three days off. He played [Monday]. At this point, we felt other steps were necessary. It wasn't working. ... There's a weakness created by the surgery. It's created an issue in another part of the knee."
Martinez, 36, is hitting .216 with only one home run. The switch-hitter is 12-for-26 (.462) against left-handers and 12-for-85 (.141) against righties.
"We're just not seeing the real Victor. We're seeing a shell of what Victor is," Ausmus said. "We told him not to pick up a bat for about a week."
Detroit has four outfielders who have been in the starting lineup for at least 14 games: Yoenis Cespedes, Anthony Gose, J.D. Martinez and Rajai Davis. Now they all might play regularly, since Martinez's designated hitter spot is open.
Outfielder Tyler Collins was recalled from Triple-A Toledo to fill Martinez's roster place.