Now we understand why Manning will be out "awhile," as Indianapolis Colts owner Jim Irsay tweeted earlier.

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Andy Lyons/Getty ImagesFor now, there's still a chance that Peyton Manning could return to action this season.

The Colts announced that quarterback Peyton Manning underwent further neck surgery Thursday, specifically a single-level anterior fusion. According to an official statement released by the team, there is no estimation of a return date, and the team will keep Manning on the active roster until it has "a clearer picture of the recovery process."

Exactly what procedure did Manning undergo? Often referred to with the acronym ACDF, anterior cervical discectomy and fusion, the surgical procedure typically involves removal of the problem disc material, implantation of a bone graft as a spacer (filling in where the disc used to be) between the two vertebrae and placement of a metal plate over the area to secure the fusion. It is called anterior because the incision is made in the front of the neck to access the spine. Advances in surgery have allowed the incision to become smaller with less trauma to the surrounding tissue.

Rehabilitation focuses on strengthening of the stabilizing muscles that support the spine along with cardiovascular exercise, range of motion for the areas above and below the fusion, and gradual progressive return to activity. Key to offloading stress from the fused segment is maintaining good mobility in other areas of the spine along with strength of the postural muscles that provide stability. As the bone healing progresses and the athlete demonstrates increased endurance, more activity is allowed.

Although the team is understandably not issuing a specific timetable for Manning's return, there is every reason to believe that he can and will return successfully -- this year or next -- after this procedure. The typical recovery time for an athlete is often two to three months, but it can be longer based on the individual and how involved the nerve compromise was. The Colts will want to see that Manning's strength has returned completely and that the fusion has healed satisfactorily before he returns to competitive play.

Dr. Joseph Maroon, who is vice chairman and professor of neurosurgery at the University of Pittsburgh Medical Center, as well as team neurosurgeon for the Pittsburgh Steelers and medical director for the WWE, has extensive experience with these types of surgeries in this population of athletes. Maroon has performed this ACDF on at least 10 professional football players and wrestlers, all of whom returned to competition. Examples include wrestler John Cena, who returned to the ring within two months after surgery, as well as former NFL players Ruben Brown and Mike Alstott, who both played for several years after their surgeries. In an interesting note, cornerback Kelvin Hayden, recently signed by the Atlanta Falcons after spending the past six seasons with the Colts, underwent a similar procedure in the offseason. Hayden had to pass the Falcons' physical to join the team, and as he told the Atlanta Journal-Constitution, "My neck is fine. … It's something that everybody was questioning. I'm just glad the Atlanta Falcons gave me an opportunity. I'm just excited to get out there and have some fun. I want to show that I can still play."

Maroon called this single-level fusion procedure "career-saving" for such athletes. Although some experienced additional neck problems down the line, they were able to extend their playing careers after surgery and intensive rehabilitation. Maroon expects Manning to be able to return without limitation as well, whenever that may be.

It only makes sense that Manning's neck, now subject to a third surgical procedure, may be an issue for him somewhere down the road. Just as many athletes undergo multiple knee or shoulder surgeries and are later forced to deal with residual degenerative changes and the discomfort that goes with it, Manning may be in line for some aches and pains later in life. After all, most football players carry such "reminders" of their former profession into their post-career years. For now, though, Manning's focus will be on recovery and return to work, something he will be only too happy to get back to doing.