UPDATE: Wednesday, August 15 at 4:35 p.m. ET
According to Ed Bouchette of the Pittsburgh Post-Gazette, Harrison has undergone surgery for his knee:
Linebacker James Harrison had arthroscopic surgery on his left knee today to remove an impairment that has caused swelling since the spring.
The surgery went well, according to one Steelers source.
It remains to be seen if Harrison will be ready for the start of the regular season.
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Harrison is currently on the physically unable to perform list due to the lingering knee problem, but the Steelers have never expressed any concern about his ability to play in the team's Week 1 game against Peyton Manning and the Denver Broncos.
His agent, Bill Parise, also remains confident he will be available for the opener despite the news of possible arthroscopic surgery between now and Sept. 9:
He’s OK. We’re just trying to make sure that we have the player we want for the regular season. Right now, James is doing all right. He’s just working through the process. If you see him, he’s probably as fit as he’s ever been. He looks great. His attitude is great. Right now, it’s just a matter of him getting that knee better.
Harrison has been one of the NFL's most intimidating and productive linebackers over the past handful of seasons. He's racked up at least eight sacks in each of the past five years, making him a key piece of the vaunted Steelers defense.
His durability has never been an issue. He's missed only 11 games since joining the Steelers in 2004, which isn't much when you consider his physical style of play.
What type of impact would missing Harrison have on the Steelers defense?
As of now, nobody involved seems to believe Harrison is in any danger of missing any of the regular season. However, whenever a player is considering even minor surgery so close to the first game, there's certainly some cause for concern.
While Harrison is a tough player and will do everything in his power to get out there against the Broncos, it will all depend on how his body reacts.
Chris Carter has been filling in for Harrison during his time on the sidelines. The second-year linebacker out of Fresno State played in just eight games last season and made only three tackles.
It would be nearly impossible for him to fill Harrison's shoes if the star's recovery doesn't go as planned, but Steelers fans shouldn't be overly concerned. At least not yet.
A final decision on surgery will have to come pretty soon with less than a month until the games actually count. Stay tuned.