"He looked like he was in pain," Sanchez said of Lee after the collision. "Anytime you hit your ribs, I think it's really painful."
Lee was taken to the hospital for tests on the left side of his ribcage and was to spend Sunday night in the hospital. A chest X-ray did not reveal any rib fractures, but Lee was still scheduled to undergo a CT scan Sunday.
"He's going to take all kinds of tests and we'll find out more," manager Brad Mills said after the game. "When you have a collision like that, we're going to get everything checked out. It might feel like ribs on the surface, but it could be something else."
Both players were chasing Mark Kotsay's pop-fly double in the seventh inning Sunday against Milwaukee when Sanchez crashed into Lee, sliding knee-first into his abdomen. Lee remained on the ground, writhing in pain, for several minutes while trainers attended to him.
He was eventually helped up and carted off the field, with his head down and breathing heavily.
Lee hit a three-run homer in the sixth inning to push Houston's lead to 4-0. The Astros scored one more in the seventh to win 5-0.
Information from The Associated Press contributed to this report.