CHICAGO -- Rays reliever Chad Bradford left Wednesday night's 4-3 loss to the White Sox with lower back stiffness despite never recording a pitch during the game.

Bradford injured himself while making his final warmup tosses on the mound with two outs in the bottom of the seventh inning. He stopped in between tosses to gather himself after feeling pain in his back, then toed the rubber once more to deliver another warmup pitch. But he signaled to Rays catcher Dioner Navarro that he couldn't throw anymore, which brought out Rays team trainers as well as manager Joe Maddon.

"Kind of out of nowhere," Bradford said of the pain. "I felt fine in the bullpen. About the fourth or fifth warmup pitch, I felt a little something grab. I tried another one and really got there where I couldn't really even move a whole lot, so then I knew I'd better shut her down.

"I've kind of been through this before. When it starts to grab, if you push it, you can really hurt something. We'll see what happens tomorrow. Hopefully it's just a bump in the road, maybe a little spasm or something. I think we'll know more tomorrow."

Bradford said there was no X-ray scheduled for Thursday and that he and the training staff would re-evaluate once he showed up to U.S. Cellular Field for the series finale.

At the time of Bradford's injury, the Rays held a 3-1 lead, with Bradford entering in relief of Randy Choate. Bradford was set to face White Sox shortstop Alexei Ramirez with runners at second and third.

After the injury, the Rays brought in reliever Dan Wheeler, who was stretched but had not yet warmed up. Wheeler surrendered both the game-tying triple to Ramirez and the go-ahead single to Jermaine Dye.