BOSTON -- As the Red Sox get ready to begin the second half of their season on Thursday against Toronto, they have a new health issue to monitor closely.

According to the Boston Herald, David Ortiz is expected to have an MRI on his right knee shortly after his return to Boston from his appearance in Tuesday's All-Star Game.

The slugger had been complaining of tightness in his right quadriceps and hamstring in the week leading up to the All-Star break. But on Tuesday, prior to the All-Star Game in San Francisco, Ortiz told the paper the root cause of the soreness is likely in his right knee.

He added that surgery may be necessary to correct what he called a 'minor' problem.

"I'm not sure, but probably," Ortiz told the paper. "I have to talk to the doctor about it and see what they want to do about it."

Ortiz went hitless in two at-bats in San Francisco and has seen his power numbers diminish significantly a season after hitting a franchise-record 54 homers in 2006. Ortiz has 14 home runs, putting him on pace to hit fewer than 30 this season. Ortiz does lead the team in doubles with 29 and is hitting .314, good for the third-best average on the team at the break.

Ortiz told the paper that he caught a cleat in loose netting around the batting cage at Yankee Stadium in the middle of last year and that could be when he initially injured his troublesome knee.

On Tuesday, ESPN.com's Peter Gammons quoted Ortiz as saying, "I think it's something they'll have to go in and fix at the end of the season. I'm trying to fight through it but some days it isn't easy."