TORONTO -- The Boston Red Sox are not sure what to expect from their most dangerous hitter, David Ortiz, when they take on the Tampa Bay Rays in a three-game series starting on Friday at Tropicana Field.

Ortiz, who hit four homers in the first three games of a four-game series against the Blue Jays, had to leave the series finale Thursday with back spasms.

He could not finish his at-bat in the ninth inning of an 8-0 loss to the Blue Jays. After checking his swing on a ball, he left in some discomfort and

outfielder Jonny Gomes took over the at-bat and hit a game-ending fly ball.

"In that final check swing, he felt some spasm in the upper-mid back, we're still examining him right now, and it's right now day-to-day," manager John

Farrell said.

Ortiz said he felt a "pop or something" in his upper back on his final at-bat in Wednesday's 6-4 loss to the Blue Jays. It had cleared up and he was able to

play on Thursday.

"I made like a rough move on that pitch, like tried to go and stop," Ortiz said. "It pulled me a little bit more today. Hopefully it's not anything serious.

We'll see how it feels tomorrow."

He did not know if he would require further time off. Friday is the anticipated rematch with Rays left-hander David Price, who hit two Red Sox, including

Ortiz, on May 30 that started a bench-clearing incident. Price said he did not like the way Ortiz admired a home run in last year's playoffs.

Ortiz could not say whether he will be able to face Price on Friday.

"I don't know," Ortiz said. "We haven't talked about it yet. ... Pretty sure I can probably come in and see how it goes. But hopefully it's nothing serious."