ST. PETERSBURG -- Andrew Benintendi was placed on the disabled list on Thursday with a sprained left knee. Marco Hernandez was called up from Triple-A Pawtucket to take his spot on the roster.
Benintendi was injured in Boston's 4-3 loss to Tampa Bay on Wednesday night while running the bases. He was on second base with no outs and broke for third on a chopper to short. The runner at third didn't run, and Benintendi had to turn back. That's when the injury occurred, and he was tagged out before being assisted off the field by trainers.
"I feel like the more I walk on it, the better it feels," Benintendi said on Thursday. "I'm going to just try and stay as positive as I can."
An MRI Thursday morning was inconclusive according to multiple reports, and the exact extent of the injury is unknown. He'll undergo further tests in Boston on Friday, and Red Sox manager John Farrell said the hope is that Benintendi returns this season. 
"It's probably too early to tell right now," Farrell said. "We're hopeful that it's not [the last we've seen of Benintendi this season]. We've just got to wait and see what comes out of this. Then depending on the findings, what is the safest thing for Andrew to get him back on the field? Optimistically, and I say that with all sincerity, it's still this year."

Benintendi's ankle wasn't hurting him at all, despite the way it buckled on the play. Farrell said he thought it was an ankle injury when he first saw it from the dugout.
Hernandez has hit .295 with one home run and five RBIs in 44 at-bats with Boston this season. The infielder has also hit .309 with Pawtucket this year. He joined the Red Sox in time for Thursday's game against the Rays at Tropicana Field. For now, Chris Young, who just returned from the DL on Monday, will be the primary left fielder for Boston, though Brock Holt will also see action there. Benintendi, Boston's No. 2 prospect per MLBPipeline.com, is now the seventh Red Sox left fielder to get injured this year.
"It's been kind of the Bermuda Triangle," Farrell said. "They're freaky injuries. Granted, this one's a baserunning injury, but still it's a left fielder. We've had a long list that have played the position. In a light-hearted moment this morning, trying to keep some levity to it all, yeah you talk about left field in that vain -- a little bit of a dark hole."

Also of note
• Eduardo Rodriguez will start on Sunday for Boston. He threw a bullpen session on Thursday and hasn't pitched since Aug. 16.