Questions with unknown answers will determine Manning's future

Here is what we know:

• Manning had surgery in February of 2010. It was a microdiscectomy performed by Dr. Richard Fessler in Chicago. Manning rehabbed and returned without incident. His '10 season was pretty good.

• Manning had similar, but not identical, symptoms coming out of the '10 season. The initial plan was to rehab and hope those symptoms cleared up.

• In May of '11, Manning had another microdiscectomy performed by Fessler, again in Chicago. He was unable to do his rehab with his preferred therapist, Erin Barill, the Colts Director of Rehabilitation, due to the lockout's restrictions.

• In July, Manning signed a five-year, $90 million dollar contract with the Colts. It is unclear whether Manning took any sort of physical before signing this contract. It is not necessary to do so.

• Manning opened training camp on the Physically Unable to Perform (PUP) list. He continued to rehab, attending practices and meetings, but not participating.

• Last week, Manning was removed from the PUP list and returned to practice. On Monday and Tuesday of last week, Manning performed "limited drills" and had no contact.

• Manning did not take part in any of the preseason games and did not dress for the fourth preseason game, the only one he was active and eligible for.

• Manning continues to have symptoms and weakness in his throwing arm. He also has soreness in his back after his practices, as reported by SI's Peter King.

Here are some of the unknowns:

Why did the surgery happen in May? For any player, the goal is always to avoid surgery as much as possible. Sources tell me the team and Manning believed he could avoid surgery with therapy and treatment, but in late April, Manning believed he was not making enough progress and elected to have the surgery. Mid-May was something of a "drop dead date," giving him plenty of time to return without missing camp given the normal eight-to-10 week recovery period. It's possible Manning believes the time prior to surgery, in which he could not work with Barill is the key period.

Though Manning was prevented from working with his preferred therapist or at team facilities after the procedure, Manning had the access and means to his choice of top-notch medical facilities, including those of Indianapolis (whose facilities are a big reason the NFL Combine is held in Indy). Still, perhaps it wasn't as comfortable; imagine going to your family doctor and finding out that he was out sick, so you have to see his partner.

What happened when Manning practiced? We're not sure exactly what Manning did during his two practice sessions after coming off the PUP list -- the Colts restricted access to those sessions at their complex. Sources tell me Manning was throwing, but that it did not seem like a normal practice. "He didn't do trees," said one source, indicating the series of routes that QBs and WRs do for timing and often use as warmups.

It's reasonable to think Manning compensated for his arm weakness by using more legs and/or back in his delivery. It's likely not conscious, much in the same way that a pitcher can adjust his mechanics when he loses velocity or has an injury. But it often leads to the same result -- a cascade injury in which protecting one part causes a change that injures another. There's also a high likelihood that Manning, with his famous work ethic and intensity, did too much in his initial workouts, leaving him sore.

The Colts say Manning will be closely monitored by doctors and would undergo diagnostics before any decision would be made about Week 1, but his status is "doubtful." That designation is meaningful as no Colts starter listed as "doubtful" on the injury report has played since '04, according to Football Outsiders' Aaron Schatz.

The next step for Manning is unclear. He is said to have lower back pain, which is easily treated, though is painful and annoying, especially since Manning is already behind in his normal preparations. The remaining symptoms in his shoulder and arm are more worrisome. Sources tell me that Manning has weakness in the triceps, an area enervated by the affected nerve. This wouldn't be corrected by more surgery. In fact, the only scenario where surgery would make sense is if the surgery from May didn't do what it set out to do.

Underlying all of this is a need to understand the microdiscectomy itself. Until the last decade, surgeons had one choice, called the "ACDF" procedure where the spinal disc was removed and the two vertebrae were fused together. For obvious reasons, an NFL player's career would be all but over after spinal fusion, and for a QB, it's just not reasonable. The microdiscectomy doesn't remove the disc, but basically creates a tunnel for the nerve to come out without being impinged by removing portions of the disc, and, if necessary, the surrounding joint. The danger is that there's further swelling or that scar tissue closes up the tunnel. It's easy enough to find YouTube videos if you'd like to see the procedure.

After surgery, the major issue is allowing the nerve to regenerate, which happens at a rate of about one millimeter a day. It's different in every person, but normally, regeneration happens quickly at first, but then flattens out. This is precisely what's being described about Manning, though it's happening at a much later date. No procedure will speed this. Speculation that there's scar tissue near the nerve hasn't been borne out, though some of the advanced diagnostic techniques Manning underwent on Monday may help determine this.

Dr. Neel Anand, the director of spinal surgery at Cedars-Sinai in Los Angeles, told me that recovery for this kind of situation can take up to a year. While Dr. Anand has not treated Manning, the type of surgery and symptoms are relatively common. "If it's pain or weakness, it's important as to whether it's new pain or new weakness," Dr. Anand explained. "Is it a new herniation in the same spot or maybe at a different level? That's a relatively uncommon outcome for this, especially in someone that's been rehabbing this long." There's no commonly used procedure that would speed up the process. "Think of it like an earthquake. The building came down on top of people, with the building being the disc herniation and the nerve being the people. Once you get the rubble cleared, is everyone ok? Some might not make it, but they've all been through something serious."

Over the next days and weeks, we're likely to hear lots of discussion of what Manning might or might not be doing. Discussions of osteopathic manipulation and plasmapheresis are already circulating on the message boards and timelines and those are just the credible concepts.

Overall, the prognosis is no different than it was a week ago. Manning is attempting to come back from a complex nerve issue. While it's hard to say "wait" (or even "breathe") to a passionate football world and an impatient, competitive QB, that's what the doctors are having to do at this stage. At this time it looks like Manning will end his consecutive game streak unless Bill Polian is working on his biggest Keyser Soze trick ever. We'll move from wondering about Week 1 to wondering about Week 2 soon enough.