ST. PETERSBURG -- The Rays were without the services of closer Troy Percival on Wednesday night, as the veteran sported a wrap around his midsection from an epidural injection performed on Tuesday.

Percival -- who has also been hampered by cartilage damage in his right knee -- will have to undergo back surgery when the season is over. For now, the plan is for the grizzled veteran to be ready on Thursday night.

Percival is scheduled to undergo two more epidural injections, which must be administered six days apart. The right-hander, who left Sept. 10's contest at Boston with back tightness, told the St. Petersburg Times he hopes to be "full throttle" for Thursday's series-opening contest with the Twins.

"Anything to finish this out," the 39-year-old Percival told the Times. "And get back to where I was at earlier in the year."

The Rays are 34-1 when Percival enters the game in a save situation, but the right-hander has struggled since coming off the disabled list Sept. 1. In his last four appearances, Percival has allowed four walks and five hits -- two of which were home runs -- totaling seven runs.

Without Percival, the Rays were likely to use Dan Wheeler or Grant Balfour if the club encountered a save situation in Wednesday's finale with the Red Sox. Wheeler's 10 saves this season have all come with Percival on the DL, and Balfour also notched three of his four saves during that time period.