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It's the final setback in what will go down as a lost rookie year for the 2014 No. 1 NFL Draft pick.
Coming out of college Clowney was the undisputed best prospect in the draft. Some regarded him as one of the best prospects in years.
He ended up making seven tackles in four games and didn't record a single sack in his first season in the NFL.
The problems started in Week 1, when Clowney tore his meniscus in his right knee after reportedly stepping in a hole in NRG Stadium's much-maligned turf. He missed six weeks.
He played in Week 8, but missed Week 9's game against Philadelphia with the flu. After he missed the Philly game, there were reports that the team was "frustrated" and want him to play through more injuries.
After missing a game again in Week 13, he visited Dr. James Andrews to get a second opinion on his original knee injury.
He told ESPN about the lingering knee injury, "I'm kind of surprised; I thought it would have been over. I thought it'd be back to where it was by now. Some people react differently to injuries."
On Thursday the team announced that Clowney will be placed on injured reserve and have surgery on his knee.
When he was healthy in college, Clowney was one of the most dominant players in the country. But he was slowed by nagging injuries and extra attention from opposing coaches during his final year at South Carolina, and he has yet to play a full, healthy game at the pro level.