SEATTLE -- Julio Lugo left Saturday night's game against Seattle in the eighth inning with what he said was a groin strain, and manager Terry Francona said he may be held out of Sunday's game as a precaution. He was replaced by Gil Velazquez.

Lugo said he sustained the injury running to first during Friday night's game, and that it tightened up on him as the game wore on. He said he probably could have kept playing if he needed to.

"More of a precaution than anything. I've been playing through it for days. It's just a little tighter," Lugo said. "Today, when I got that hit to left field, and tried to go to second, it got tight then. Through the course of the game, it got a little tighter. But I'm going to work it out," Lugo said.

Bringing in the slick-fielding Velazquez certainly did not hurt Boston's defense as it protected its lead, however; Lugo already had a throwing error earlier in the game.

Francona said the injury may be to the hip flexor, not the groin, but he said regardless, he didn't think it was serious.

"We'll re-evaluate him in the morning. With a day off [Monday] we'll probably try to stay away," Francona said.

On a one-to-10 scale, Lugo rated the pain fairly highly.

"It's about a six -- but I think it will calm down tomorrow," he said.