BOSTON -- Red Sox right fielder Mookie Betts exited Friday night's 2-1 loss to the Twins with right knee soreness in the fifth inning and is day to day. He was replaced by utility man Michael Martinez.
Red Sox manager John Farrell said the soreness was something Betts has been feeling since the All-Star break, but it didn't impact his ability to play until Friday.
"He got a little soreness, a little stiffness as the game went on," Farrell said. "Felt like he couldn't run as normal. Precautionarily we got him off his feet. We'll check him when he comes in tomorrow to see if he's going to be available. Right now, day to day."
Betts went deep on the second pitch of the first inning against Kyle Gibson for an early Red Sox lead. It was his fifth leadoff home run of the year and 20th home run of the season. Betts grounded out to third in his second at-bat before leaving the game with the score tied at 1.

Farrell said Betts' knee was occasionally getting treatment before Friday, but it was never troublesome enough to leave him out of the starting lineup.
"This isn't the result of a slide or any one event. He just felt like there was some soreness starting to come on," Farrell said. "At the time that was the decision made."
The manager said if an MRI is necessary, the Red Sox wouldn't take any risks with Betts.
The right fielder is having a standout year, hitting .307 with 26 doubles, four triples and an .879 OPS. He has seven hits, including five extra-base hits, in his last three games. Betts has seven career leadoff homers, and Friday marked the second time this season he's hit a leadoff blast in back-to-back games.
Even though Martinez had big shoes to fill, he adjusted smoothly to right field by making two impressive defensive plays. The first came in the sixth inning when Eduardo Escobar popped up in foul territory. Martinez sprinted in from right field to end any further damage by the Minnesota bats.

"It felt great," Martinez said about contributing. "I just have to stay prepared. When they put me in, I just wanted to do my best to help the team in any way I can."
Martinez had only played 14 career games in right field before taking Betts' spot on Friday. But the utility man made another outstanding defensive play on a lineout to right to start the eighth inning.

The 33-year-old likes playing in right field because of his mobility and speed in that spot.
"The one thing that Mike does, his work pregame keeps himself sharp," Farrell said. "Of the three outfield positions, right field is clearly his best. That was the report even coming over from Cleveland. Makes a couple of nice plays -- a running catch to end the inning and the diving catch to lead off the eighth. Good bat to ball. Athletic guy. A valuable skill set."