Colvin, a former North Augusta and Clemson standout, was standing on third base in the second inning of Chicago's 13-3 victory at Florida when he was struck by a sliver of Welington Castillo's maple bat. Castillo doubled on the play and Colvin scored, but was replaced in the field in the bottom half.
"I feel really bad about it," Castillo said. "It wasn't on purpose, but he's my teammate. I hope he's getting better."
A Cubs spokesman said Colvin was in stable condition at Jackson Memorial Hospital and is expected to remain there for the next few days for observation.
Colvin was watching Castillo's liner into the left-field corner and looked surprised when he was hit by the bat.
"These bats, I'm amazed it doesn't happen more," Cubs manager Mike Quade said. "We have seen guys get hit with pieces, but to actually get stabbed with one, I just don't ever remember (seeing it)."
A Cubs trainer said Colvin was hit in his upper right chest, allowing air into his chest well and potentially into his lungs. He had very little external bleeding.
Colvin was being treated with a chest tube to prevent a collapsed lung.
The right fielder is expected to miss the rest of the season. He hit .254 with 20 homers and 56 RBI in his first year in the majors.