Sanchez was injured when the Phillies' Rod Barajas slid into his knee as he was turning a double play at second base in the fourth inning.
Sanchez stayed down for about three few minutes, then walked off the field accompanied by a trainer. He spent about half an hour in the trainer's room, told reporters that he was OK and was scheduled for an MRI exam.
"As of right now, it just feels like a bruise or something like that," Sanchez said. "It's nothing big."
A test showed a mild sprain of the medial collateral ligament.
"You take a deep breath, obviously. A huge one," Pittsburgh manager Jim Tracy said. "I had my fingers crossed."
Sanchez, who hit .344 last season, is day to day. He didn't complain about the slide.
"I'm a big contact guy, and I don't shy away from it," Sanchez said. "It is spring training, I know. But you're still trying to get ready for the season."
Barajas felt that Sanchez did not do enough to get out of his way.
"I'm taught to go hard to second to break up two, and that's what I did," Barajas said. "I didn't come up high, and my spikes weren't up. I slid the way I've always been taught. Unfortunately, he didn't get out of the way."
Brad Eldred homered for Pittsburgh -- he's homered in all four games he's played.
Pirates starter Ian Snell struck out seven but allowed three runs, three hits and two walks in three innings.
Ryan Howard hit a two-run double in the third. Karim Garcia had a two-run single later hit the inning and Barajas hit a three-run double off Tom Gorzelanny, who gave up six runs -- five earned -- and five walks 1 2-3 innings.
Philadelphia, which led 9-0, allowed five runs in the ninth, got a two-run single from Brennan Kings in the 10th, then allowed Eldred's home run before Jeff Farnsworth got the final two outs.
Philadelphia made five errors.