Tim Lincecum returned to the mound for the San Francisco Giants on Wednesday night, recording five outs of scoreless relief.
However, he left Game 2 of the World Series with tightness in his lower back and is day to day.
"I felt good. It was nice to get out there and compete a little bit, but outside of all that, what I'm really thinking about now is hurting myself," Lincecum said. "It's all right now. We're just going to treat it and see how it feels tomorrow. But right now it just feels pretty stiff."
Brought into the game in the seventh inning with San Francisco trailing by five runs, Lincecum retired the first five batters he faced, striking out two of them. Then he suddenly left the game.
"The pitch before the last one, I felt something tighten up in my lower back," Lincecum said, adding that it was more stiffness than pain. "I just decided not to go any further."