James Harrison (left) may have to have arthroscopic knee surgery before the Pittsburgh Steelers’ regular-season opener. (Gene J. Puskar / AP)

Updated at 4:30 p.m. with report that Harrison had surgery today.

Pittsburgh Steelers linebacker James Harrison underwent arthroscopic surgery on his left knee this morning, which raises the possibility that he might not be available for the season opener Sept. 9 against Peyton Manning and the Denver Broncos.

A source told Pittsburgh Post-Gazette reporter Ed Bouchette that the scope “went well,” but the Steelers have not indicated how long Harrison could be out. Prior to the procedure, Harrison’s agent, Bill Parise, said Harrison could have arthroscopic surgery and still be ready for the “Sunday Night Football” opener in Denver in a little over four weeks.

Harrison was dealing with swelling in the knee, the Beaver County Times reports, and it raises the question of why the surgery wasn’t done earlier. Harrison has been bothered since minicamps and has been on the physically-unable-to-perform list since training camp opened.

Parise previously indicated that the team’s plan is to take Harrison off the PUP list in the next two weeks and, if swelling continues, he would have surgery. Parise believes Harrison, 34, could play within a week afterward.

“With the exception of this little knee thing, James is probably healthier now that he’s been in three years,” Parise said. “He’s extremely fit. He just has to get this irritation behind his kneecap cleared up. That’s what’s causing the swelling, and [the Steelers] just want to get rid of that. 

“So we might even look at doing a scope of that to get it cleaned up. We’ll just have to wait [and] see how it plays out.”

Manning probably wouldn’t mind not having to face the NFL’s Defensive Player of the Year in his first NFL game in about 20 months.

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