Manning missed the entire 2011 season after having what was thought to be his third neck surgery in less than two years. There have been conflicting reports about how much progress he has made in his attempt to return for the 2012 season.
However, according to SI.com's report, Manning had a fourth procedure after his May 23 surgery to fix a bulging disk and before his neck fusion surgery Sept. 9. According to the website, the same surgeon who handled the bulging disk procedure also handled this previously unreported follow-up procedure.
SI.com, citing league sources, reported that all four of Manning's procedures were to the right side of the quarterback's neck.
Manning's agent, when reached by SI.com, wouldn't go into specifics on the quarterback but said, "I wouldn't have anything to say about all of that, one way or another.''
The Colts owe Manning, who turns 36 in March, a $28 million roster bonus by March 8. They want to use the No. 1 pick in this year's draft on Manning's successor, and the future of their star quarterback will affect how much room they'll have under the salary cap.
Colts owner Jim Irsay said Tuesday that he plans to meet with Manning within the next week but is leaving the door open for Manning to stay with the Colts.
"We want this to be his decision," Irsay told ESPN on Tuesday. "We want him back if he wants to come back. We can work out the contract if he wants to work it out. It's going to be Peyton's call."
If the Colts decline to pay Manning his bonus, he becomes an unrestricted free agent.
"It's a two-pronged thing," Irsay said. "The first is if and when the nerve regenerates and whether it allows him to play at a high level. But I always want Peyton to understand the risk-rewards about playing. We want to make sure he understands the long-term aspects of his health in trying to play."
If Manning wants to stay, Irsay said they could find a financial way to make it work.
"We can work out the contract if he wants to come back," Irsay said. "We want him to make the call. He's earned that. We want him to have the chance of finishing his career here if that's what he wants to do."
SI.com also reported Wednesday that Manning wanted to try to play in the Colts' home finale against the Houston Texans in Week 16, even going through a scripted 30-play practice in the week before Indianapolis' Week 15 game against the Tennessee Titans. Then-team president Bill Polian, former coach Jim Caldwell and ex-offensive coordinator Clyde Christensen were at the practice.
Manning had hopes to at least play in red-zone situations, where his weakened arm strength wouldn't be a hindrance.
Sources who were at the practice told SI.com that Manning's passes to running back Joseph Addai and practice-squad receivers were accurate at the session, but that he couldn't throw anything longer than 22 yards. His passes also sometimes wobbled, according to the sources, who estimated that his velocity on the passes was around 80 percent of his normal throwing speed.
The practice session was moot, however, as team physician Hank Feuer wouldn't clear Manning to return to action.
"He wanted to go on the field and try to dump red-zone passes against Houston,'' a league source told SI.com. "Even though his neck muscles hadn't even been strengthened yet. Can you imagine anyone putting him on the field in that situation? Just to throw a string of red-zone passes? But that's where things were going at that time, and it kind of speaks to the insanity of the situation.''
Information from ESPN.com's John Clayton and The Associated Press was used in this report.