Jennings, who was the National League Rookie of the Year in 2002, hurt his right middle finger Wednesday against Washington while making a hard slide into second base trying to break up a double-play.
"Jennings has a compression fracture of the middle finger of the right hand," said Colorado Manager Clint Hurdle, who made the announcement before Friday's game against Pittsburgh. "He's out for the season. That's not what we would have put in for, but it's what we got."
Jennings finishes the season with a 6-9 record and an ERA of 5.02 ERA. Only he and left-hander Jeff Francis (8-7) have been in the club's rotation all season.