The report has been confirmed by the Associated Press.
The healing process from that surgery proved to be frustratingly slow, and after consulting with half a dozen neurosurgeons, it was decided that the best course of action for Manning was to have a one-level cervical fusion in his neck. In short, cervical fusion is when surgeons remove a herniated disc and put a bone graft in its place.
Manning had been hoping to avoid the procedure that put him out for that long, but eventually, it proved inevitable. "I think he's OK, probably because there's a little finality to this deal in terms of playing," Manning's father Archie told Mortensen. "He's been on the clock since May. He didn't make it. Obviously, it's a big letdown, but he can relax a little bit compared to the intensity of everything he has done trying to rehab."
Manning's brother Cooper told ESPN that "everyone is different, but I've had a fusion and I've known players who have had fusions and went on to play football. ... You can get a pretty good range of motion back and much more stability once it heals."
But at least one medical expert — SI.com's Will Carroll — believes that such a surgery could be potentially career-ending.
The Colts had originally taken Manning, who recently signed a five-year, $90 million contract extension, off the physically unable to perform list so that he could practice. However, back troubles exacerbated his previous issues, and it was back to the doctors for more diagnosis.
On Thursday morning, Colts owner Jim Irsay tweeted that Manning was going to be out "for a while," which may be a conservative estimate. At some point, a decision will need to be made about the wisdom of having Manning playing at all this season, something that Hall of Fame defensive end Howie Long spoke to Yahoo! Sports about on Wednesday.
"When the lights go out at night, and an athlete's staring at the ceiling, one thing that is probably their biggest fear is the neck," Long said. "For a number of reasons, and some of them are obvious. When you start to get into multiple neck procedures, you're getting into nerve damage, and you're getting into the spinal column. It's a scary proposition, and it's certainly not a good thing.
"Will he be back this year? Hopefully, he is. But my point is this — when you're into multiple neck issues, it doesn't get better.
"I don't know where he is, and only Peyton knows that. And it sounds like the medical staff was trying to determine why the process was going slower than they had anticipated. I think it's important that Peyton does what's best for Peyton."
The Colts will move forward with veteran Kerry Collins, who had recently retired, as their starter. They face the Houston Texans in Houston for their season opener this Sunday.
"It's a good thing none of them play for us," Colts center Jeff Saturday told the NFL Network, when asked about the volumes of people who don't believe the team can win without Manning. "We still have to show up on Sunday and take on the Texans. With or without Peyton, we still have to show up and play. Obviously I'm disappointed. He's one of my close friends, I'm sad for what he's going through, but we have a job to do and that's to go down and beat the Texans and get a division win in Week 1."
"He deserves all of the credit he's gotten. The guy is the greatest quarterback to play in our game, but the reality is that he's not here now. He's trying to get healthy and get back as soon as possible, but I have a little chip on my shoulder. I think as a team we have a little chip on our shoulder. We need to go out and show the world that we can keep winning games and keep us in this playoff hunt until he finally does get back and gets a chance to get behind the helm.
"At the end of the day, there are going to be 53 guys ready to play come Sunday and we need to get a win."
Other popular stories on Yahoo! Sports:
• Higher Education: The real rarity of Peyton Manning
• Peyton Manning's injury could shift $65 million in fantasy winnings
• NFL's most valuable teams
- Peyton Manning