Paul Tracy, 37, the 2003 series champ, broke a shoulder blade in an ATV accident near his home in Las Vegas on Oct. 28. He began rehab almost immediately, but a setback in recent days effectively ended hopes he could add to his consecutive starts streak that stands at 136 races.
"That would have been a lot of experience for both me and David to draw off of once we got down into Mexico," Rice said in a teleconference Tuesday.
Tracy may not feel well enough to travel south of the border to be a spectator, Rice said. Tracy is fifth in the standings in a season clinched by Sebastien Bourdais.
"I'm very disappointed, obviously," Tracy said in a statement. "It's been a long season. I've done Grand Am races, NASCAR races. I've done a lot of tests, so for now the best thing is to relax and let my shoulder heal. I don't want to risk hurting it even more."
Rice was hired Oct. 26 to replace A.J. Allmendinger, who signed a multiyear deal to run with Team Red Bull in NASCAR.
"At the end of the day, I'm going to put myself in a position to drive a competitive car," said Rice, who is only signed with Forsythe for Mexico City at the moment. "That's what my whole goal is right now, and I've been given that opportunity. We'll see where that goes from here."
Rice, the lone U.S.-born driver expected to be in the field at Mexico City, was notified in July that he wouldn't be brought back by Rahal Letterman Racing, an IRL team he led to the 2004 Indianapolis 500 title.
Martinez drives in Champ Car Atlantic, the main feeder series to Champ Car that Rice had been a part of before he veered into the IRL. Had Tracy not been injured, Martinez would have been in a third car for Forsythe.