Let's stipulate a couple things up front.
1. There's no real way to compare two very different surgeries.
That said, let's get the facts down on pixels before the voters put things down in ink. In a vote this close, it really is a valid "tiebreaker" to say which player had the longer, more difficult journey back to the pinnacle of the NFL. It's more important for the comeback award, for obvious reasons, but I get the sense that the vote is just that close in MVP as well.
So which one had the tougher road?
Peyton Manning had a single-level anterior fusion (SLAF) in September of 2011. The herniated disc was causing the nerve coming out of his spine to be impinged ("pinched") which created weakness in both his shoulder and his hand.
Two of the top spinal surgeons in the world, Dr. Robert Watkins and Dr. Robert Watkins Jr. (yes, they're related), performed the surgery to fuse two vertebrae together through a small incision at the front of his neck. (The scar is visible, just to the side of Manning's Adam's apple, though I could not find a clear picture of it.)
The fusion was successful, using titanium hardware and a small block of bone from Manning's hip. Manning was cleared by the surgeon in January.
Manning previously had two surgeries—both posterior microdiscectomies. The scar is more visible, with one on either side of the spine, at slightly different levels. In these procedures, the surgeon took a small "tunnel" out of the herniated disc to reduce stress on the nerve. The first of these surgeries were successful and Manning was able to play after the first procedure, having a pretty darn successful 2010 season.
The second surgery, in May of 2011, did not have as good of results.
There are reports that Manning had a setback during workouts, but it's more likely that Manning's second surgery did not provide results that held up long term. Sometime prior to his September fusion, Manning went to Switzerland for Orthokine therapy. This involves injections of Manning's own manipulated blood back into the affected area. The procedure is not approved for use in the U.S., but this does not mean it uses any banned substances.
Several athletes, including Kobe Bryant and Alex Rodriguez, have had similar procedures; PRP (platelet rich plasma) injections, which are similar, are growing in use in the U.S. sports medicine community.
Dr. James Andrews told me in January that he was increasing the use of PRP in his patients with shoulder and elbow problems. "I'm not sure if it works, but it sometimes gets good results and it's not hurting anyone," he said during lunch at his Injuries in Baseball Course in Birmingham.
This third procedure, the Orthokine injections, is often referred to as a "third surgery." This is a misnomer. The procedure is little more than having blood drawn, then injected back in. If this is surgery, then painkillers are as well, meaning half the NFL is having pregame surgery each week!
Once the fusion was solid, Manning had to wait for the nerve to "regenerate." The procedure was described to me by an NFL team doctor as more akin to having your foot fall asleep and then wake up. "The nerve is stressed, pinched for months, maybe years, and now it's freed up. It takes it a while to come back and it doesn't do so predictably."
Manning saw this, with some problems in initial workouts, leading to his release by the Colts; but then saw rapid jumps in ability during his workouts with Duke coach David Cutcliffe.
By the time he signed with the Broncos, Manning's arm strength was at 80-85 percent according to some that saw him throw live. Manning adjusted his mechanics and avoided some of the more difficult throws early in his return, but by the end of the season, he showed no hesitation with deep outs, which were the last to return.
On the other side of this is Adrian Peterson, who spent New Year's Eve in a hospital bed in Gulf Breeze, Florida. He had just had his ACL reconstructed by Dr. James Andrews at his palatial Andrews Institute near Pensacola. Peterson had also torn his MCL, but this was not repaired, merely cleaned up.
Using normal surgical techniques, Peterson was in rehab on New Year's Day.
ACL surgery, until recently, has been given a standard recovery period of 12 to 18 months. New techniques in rehab, as well as genetics and Peterson's exceptional physical conditioning, also helped in his return. By January, Peterson was ahead of schedule and showing confidence in the knee. That confidence and proprioception—the ability of the body to sense its place in space—never seemed to leave Peterson, though it is usually the last thing to return.
By April's minicamp, Peterson was sprinting and showing no deficits.
It's possible that Peterson could have suited up for an NFL game at that point, though he would have been at risk of further injury. By August, he was clearly ready but the Vikings were very cautious. All this makes the "eight-month return" a bit dubious. We don't know exactly when Peterson could have returned.
Nor is this kind of return singular. You might remember Wes Welker returning on a very similar schedule and playing very well, though he clearly did not have the same confidence in his knee all through the season. Peterson's rehab was just done with an exclamation point, returning to one of the best offensive seasons ever. It was a relatively routine surgery with a long, targeted rehab.
Both of these exceptional athletes had medical care that was just as exceptional. Both worked hard in rehab, regaining position and sport specific skills. While Manning's surgery took place three months earlier, there was very little work he could do until his surgical clearance in early January, which makes the timelines similar.
Was one harder? Was one less predictable? Well, now you have the facts and you can decide.