Beltran started all three games of that series, May 22-24, at Fenway Park as the designated hitter. He started one day later against the Nationals before being sidelined for two nights to rest the knee. A subsequent bout with a stomach flu extended his absence from the lineup.
The injury affects Beltran most when he runs, especially when he slows down from a sprint.
"Every time I run, I feel a pinch. It's annoying," Beltran said. "At the plate, I don't feel anything."
Beltran's main concern is whether the injury will get worse if he keeps playing on it. If not, he plans to continue playing while managing the pain.
"I've been able to go out there feeling like that and do fine," Beltran said. "If it's something that's going to get worse, I can't keep playing."
The Mets can ill afford to lose Beltran's bat. As is, the team is missing leadoff hitter Jose Reyes with a slight tear in his right hamstring and cleanup hitter Carlos Delgado after right hip surgery.
Tim Britton is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.