The Boston Red Sox sidelined slugger Mike Napoli with a sprain in his fourth finger on his left hand, the team announced on Sunday.

Napoli, who is batting .260 with 22 RBIs and 5 homers, is placed on a 15-day disabled list and it's not expected to return until the injury is completely healed, according to Red Sox manager John Farrell.

"Mike was still a few days away," Farrell said in an interview with ESPN. "We wanted to give him ample time with the finger, but given the situation and the need for an added arm, we felt like we had to make the move to put Mike on the DL.

"Hopefully this gives him that extended period of time to get past this in its entirety, or at least to try and get further ahead of it."

The Red Sox are very much concerned about the recovery of one of the most important sluggers on their lineup. Since suffering the injury, Napoli hasn't been the same slugger he was.

"It's impacted [him]," Farrell said before Saturday's loss. "To what extent, it's hard to say, but ever since the injury it's pretty clear. He's not one to make excuses, but at the same time coming off the flu and everything he's dealing with, he needs at least a couple more days. This isn't a one-day thing; we're hopeful it's not 15."

The Red Sox are currently in the bottom of the American League East standings with a 21-29 slate.