The reason is simple: Indianapolis doesn't want to take away practice snaps from quarterbacks Dan Orlovsky or Curtis Painter with the Colts (1-13) hosting the AFC South champion Houston Texans (10-4) in their home finale Thursday night.
Caldwell said he also believes Manning will be better off recovering from his latest neck surgery through individual work.
Colts vice chairman Bill Polian acknowledged that Manning will fail his postseason physical, a move that actually will give the team more time to monitor the quarterback's progression since he can rehab with other injured players at the facility. Colts officials say it isn't a setback; in fact, Polian said Manning threw with decent velocity from 20 to 25 yards last week.
"He has to meet objective measurements set by the doctors and the rehab people with respect to arm strength, with respect to triceps strength and that will be evidenced by throwing and other objective measurements," Polian said.
It's still unclear when Manning might be 100 percent.
"I do not know," Polian said. "I've said since September, and I've quoted the doctors, all of the doctors we've spoken to, that there's no potion, there's no surgery, there's no manipulation, there's no machine that can tell you what the timetable for regeneration of a nerve will be."
Caldwell, Polian and team owner Jim Irsay do need to see some things before March 8, when the Colts must determine whether to pay out a $28 million bonus to keep Manning or let him become a free agent. Irsay also has acknowledged there's a third option: redoing the five-year, $90 million contract Manning signed in July.
Manning hasn't participated in a team workout since having a single-level fusion procedure Sept. 8, the third and most invasive of his neck surgeries over a 19-month span. The perennial Pro Bowler hasn't spoken with reporters since Dec. 2, the day after he was cleared to increase the intensity of his workouts.
Last Wednesday, Caldwell and Polian both watched Manning take snaps from center Jeff Saturday and throw to running back Joseph Addai, wide receiver Anthony Gonzalez and an unidentified receiver from the practice squad during a post-practice workout. Manning is expected to do that kind of work over the next two weeks.
Copyright 2011 by The Associated Press