The left-hander left his last start Saturday night after hurting himself. He was scheduled to test his groin in a bullpen session Tuesday, but that was canceled.
"Our medical people had been working on him over the last couple days and his groin is about the same as it was when we had to remove him from the game Saturday night in Los Angeles," Rockies manager Jim Tracy said.
De La Rosa led the majors with 16 wins after June 1. He lost his first six decisions, and finished 16-9 with a 4.38 ERA.
If the Rockies beat the defending World Series champion Phillies, De La Rosa could return for the NLCS.
"I think that's definitely a viable possibility," Tracy said.
Ubaldo Jimenez (15-12) will pitch Game 1 against the Phillies on Wednesday. Aaron Cook (11-6) is scheduled to start Game 2. Tracy gave Jason Hammel (10-8) the nod for Game 3 over All-Star Jason Marquis (15-13).
"Jason Hammel has stepped up and has pitched extremely well during the course of the second half of the season," Tracy said. "He has been a guy that in big games against ones and twos in other club's rotations, has not only won games but has put us in a position to win some of these games that he was not involved in the decision."
Marquis will pitch out of the bullpen in the first three games. The right-hander was 4-7 with a 4.56 ERA in the second half after going 11-6 with a 3.65 ERA in the first half.
"I think the first two-thirds of the season were exceptional," Tracy said. "Right now he's not throwing the ball quite in the same manner. And to ignore a guy that has thrown the ball as well as Jason Hammel has thrown it since the All-Star break, I really feel is doing ourselves a disservice."