An unsettling possibility hit the sports world on Tuesday night: one of the most talented athletes we've seen in years may have already played his best football.

Jadeveon Clowney requires a nine-month recovery period after undergoing microfracture surgery Monday on his right knee. That sidelines the Houston Texans' No. 1 overall draft pick into September. What's far more troubling is that a return to his former level of dominance is more of an "if" than a "when."

Jadeveon Clowney played in only four games this season for Houston. (USA TODAY Sports)

"We're trying to convince the body to do something it's not designed to do," said UCF team doctor Michael Jablonski, who has performed microfracture surgery and trained under renowned surgeon James Andrews. "It doesn't work every time."

Here's how microfracture surgery works to repair the knee and why it's not a sure bet to fully fix Clowney's problem:

The procedure is called "microfracture" because an awl is used to poke holes in the bone surrounding the knee. These tiny punctures are meant to stimulate blood flow to repair torn cartilage in the area. This has to be done because the human body doesn't regenerate cartilage on its own. So the blood brought in by the microfracture surgery can ideally latch on to the injured area and help protect the bone.

Jablonski compared the missing or torn knee cartilage to a pothole, and the microfracture surgery can fill it with the equivalent of sand.

"It's not as strong," he said. "When athletes are putting a lot of stress on those areas, sometimes it deteriorates because it's not designed to deal with the forces."

So Clowney will likely not be able to bear weight on his knee for weeks, and not be able to run for months. It's not a guarantee that the procedure will work even after all that, and it's not a guarantee it will hold up even if it works. Clowney will need to deal with the frustration of a long process, and the fear of an imperfect rehab.

"If you were to ask me if I'd rather an athlete tear his ACL or have this problem, I would take the ACL tear," Jablonski said. "It's much more likely he would come back at the same level with an ACL."

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This doesn't spell doom for Clowney. Reggie Bush and Marques Colston, among other NFL stars, have returned to have long careers after microfracture surgery. Kobe Bryant and Amar'e Stoudamire have also recovered and played at a high level.

Running back Reggie Bush had microfracture surgery in 2008. (Getty Images)

"For every person who has come back at a high level," Jablonski said, "there's another one who didn't."

The easy (and feared) comparison is Greg Oden, the No. 1 overall pick in the 2007 NBA draft. He's never been the same player since his surgery, and we're left to wonder how good he really could have been. It's the same with Courtney Brown, who, like Clowney, came out of the state of South Carolina and rose to the No. 1 overall pick in the NFL draft. After being taken by Cleveland in 2000, he had only 17 sacks for the Browns. A host of setbacks, including microfracture surgery, derailed his career that ended after the 2005 season.

That's a harsh parallel not only for the Texans, who chose Clowney first in a stacked class of rookies this year, but also for the football world. It was thought that Clowney might be the next Lawrence Taylor – an unstoppable pass rushing force that would make All-Pro defensive lineman J.J. Watt even more dominant.

Now the hope is merely that Clowney will resemble the lion who put fear into the eyes of quarterbacks at South Carolina. Brown's 17 sacks are a sad statistic in retrospect, but Clowney hasn't had a single sack in his short pro career so far.

"Even if it's super successful, it's not normal cartilage," says Virginia-based orthopedic surgeon Derek Ochiai. "When you do it, you're hoping the cartilage is good enough that the knee can function close to normal. It's not like you're making that knee perfect."

The next several months will be crucial for Clowney's career. And you don't need to be a Texans fan to hope to see his potential fulfilled when he returns.