Yet after he missed the entire 2011 season, doubts swirled early and often.
Yeah, and I saw him after that first surgery, this neck surgery, and I was pretty much convinced that he was done. There was no way he could come back and play football. That first time he went and we were just throwing it in the backyard of our house. We're throwing 15 yards away, and it was a lob. He couldn't throw 15 yards on a line. It had no pop. I was like, I mean -- he wanted to come back and play football, and I didn't think it would happen.
So much for that.
Not only did Manning win the 2013 NFL MVP, he also broke both the single-season passing touchdown (55) and passing yard (5,477) records on the way to leading the Broncos to Super Bowl XLVIII—all in just his second season back from injury.
Thank you, Dr. Robert Watkins.
Watkins, one of the best spine surgeons in the world, resuscitated Manning's career in every sense of the word, as he has so many other athletes'.
Now what? At age 37, will Manning return for the 2014 season?
According to ESPN.com, sources told ESPN's Chris Mortensen that much depends on a looming physical exam scheduled for March:
If the exam reveals that his neck is stable, Manning plans to return to the Broncos in 2014, regardless of how Denver fares this postseason, according to sources.
But if there is an increased risk of injury, Manning will be forced to decide whether to retire, sources said.
In order to understand what Watkins will be looking for, let's crack open the anatomy textbook, starting first with a brief look at the biggest of the four surgeries itself.
The Surgery: Anterior Cervical Discectomy and Fusion
After undergoing other, less-invasive procedures aimed at reducing pain, Manning underwent an anterior cervical discectomy and fusion (ACDF) in 2011. Surgeons use ACDFs to alleviate pressure from a bulging cervical intervertebral disc—the cartilage cushion between two spinal vertebrae.
Two different types of material compose an intervertebral disc. On the outside sits a ring of relatively tough material known as the annulus fibrosus. Inside of it lies the jelly-like nucleus pulposus.
For a better picture, imagine a jelly donut. The jelly represents the nucleus pulposus, and the bread represents the annulus fibrosus.
With enough time and trauma, intervertebral discs can wear down. Eventually, the nucleus pulposus leaks through a weakened annulus fibrosus—or "herniates"—causing inflammation and placing pressure on nerves as they leave the spinal cord.
Compressed nerves in the cervical spine can then lead to weakness, numbness and pain in the neck, arms or shoulders. Ideally, by removing the offending disc, doctors cut out the root cause of the problem, thereby allowing the damaged nerves to regenerate and regain function.
After removing the disc, a surgeon will then use metal hardware to fuse together the vertebrae that rest immediately above and below the resulting gap. Doing so enhances cervical spine stability.
Additionally, the surgeon often removes pieces of bone from the athlete's hip and places them in between the fused vertebrae to stimulate bone healing and fusion.
Offseason Benchmark No. 1: Pain
As mentioned, the removal of a herniated disc relieves pressure on the surrounding nerves. Pain—previously starting in the neck and radiating into the arms or shoulders—then lessens with time.
In Manning's case, after surgery, it lessened sufficiently enough to allow him to return to the NFL for at least two years.
Yet what about in 2014 and beyond?
Following an ACDF, pain can return. For instance, different discs can follow a similar course as the one addressed by the ACDF. Arthritis may also develop within the spine.
The stresses of Manning's career in the NFL only speed up such processes relative to the general population. Steroid injections and other measures can further temporarily blunt the pain, but once it begins to limit his throwing and effectiveness on the field, he may need to hang up his cleats once and for all.
As of now, only Manning and his doctors may know if or when such a scenario will come to pass.
Offseason Benchmark No. 2: Strength
During ACDF rehabilitation, not only must injured nerves recover, but the muscles they control must as well. Eli Manning's aforementioned remarks suggest he caught his older brother in the very early stages of his recovery process.
In other words, it doesn't matter how strong a muscle is if there is no nerve signal to tell it to fire.
This offseason, a decrease in arm or shoulder strength on one side relative to the other—as measured by anything from basic physical exam maneuvers to more specialized tests—may suggest new or recurring problems within Peyton's spine.
If decreasing strength begins to affect the speed, power or accuracy of his throws, Manning and his medical team will need to closely evaluate the indications, risks and benefits of further medical intervention aimed at prolonging his career.
Offseason Benchmark No. 3: Sensation
Whereas the brain uses nerve signals to the contract the triceps, biceps and deltoids, nerves also carry sensory signals back in the opposite direction.
When returning signals reach the brain's primary sensory cortex, it can interpret, for example, the rough surface of a football. On the other hand, the cerebellum lets an athlete know where, for instance, his index finger rests in three-dimensional space through a process known as proprioception.
If nerve signals cannot properly move through an area of compression in the spine in order to reach the brain, numbness and tingling can arise.
Not being able to fully feel a football can lead to fumbles or a poor grip, as can a poor sense of where one is in space—and thus the throwing motion.
Offseason Benchmark No. 4: Cervical Spine Stability and Long-Term Health
Reigning above all else is Manning's long-term health and well-being.
Nothing else comes close.
An unstable cervical spine may place an athlete at higher risk of serious injury. Doctors must look closely for any ligament laxity in or around the spine that could predispose to further damage should he sustain large enough trauma to the head or neck.
How do doctors determine the degree of cervical spine instability that may exist? Dr. Neel Anand, director of spine trauma at Cedars-Sinai Spine Center in Los Angeles, weighed in on how to make such a diagnosis—or not:
Currently, there is no clinical exam to determine instability for the cervical spine. The most effective means for determining instability are results procured from x-rays, where we ask the patient to bend forward and backward, as well as MRI and CT scans. A dislocation or three column injury indicates instability or an unstable spine. The MRI or CT scan may also discover neurological issues which may also help us conclude instability.
In other words, certain radiographic abnormalities can imply spinal instability, but no physical exam techniques are diagnostic.
With that in mind, Manning's March exam will likely consist of not only doctors exhaustively testing Manning's strength and sensation throughout his upper body, but also thorough imaging studies.
If he passes all of the necessary checkpoints in Dr. Watkins' expert opinion—pain, sensation, strength and stability—it seems the future Hall of Famer will almost certainly take the field for his 16th year in the NFL this coming Summer.
If he wants to, that is.
Dr. Dave Siebert is a resident physician at the University of Washington who plans to pursue fellowship training in Primary Care (non-operative) Sports Medicine. All quotes were obtained firsthand unless otherwise noted.