OAKLAND -- Rays closer Troy Percival had to leave Thursday's game against the A's in the ninth inning because of a right knee sprain.

Percival will visit a doctor in Texas on Friday, but the outlook does not look good, as he wore a brace and had a set of crutches in his locker after Thursday's 7-6 win.

With Percival likely headed to the disabled list, the Rays plan to fly a relief pitcher, who would be activated if the prognosis is bad, to Texas. Likely candidates include left-hander Kurt Birkins and right-hander Juan Salas from Triple-A Durham, both of whom are on the 40-man roster. Bulls right-hander Scott Dohman could also be a possibility, but a player would have to be taken off the 40-man in order to make a spot for him.

Percival's injury occurred in the bottom of the ninth. Jack Hannahan drew a leadoff walk against Percival before moving to second on a sacrifice bunt by Mark Ellis. Percival fielded the bunt and chased down Ellis, but injured himself in doing so and had to leave the game.

"I made the play -- I never felt anything pop," Percival said. "It's not the hamstring; it's my knee. When I was walking back to the mound, I felt some sharp pain going on in there and I couldn't put weight on it. It's a sprain of some sort. I don't know."

Percival already has had two stints on the disabled list this season due to a left hamstring problem.

"I'd like to give you a medical opinion," Percival said. "But I have no idea."

Pressed further for a gut prognosis, Percival replied: "I don't even like to give those any more, because my opinion is I'll be back out there in two days. And most of the time, it doesn't work out that way."