Harrison underwent arthroscopic surgery on his left knee Wednesday, a source with knowledge of the surgery told NFL.com and NFL Network's Albert Breer. Coach Mike Tomlin later confirmed the surgery took place Wednesday, terming it "minor," but wouldn't offer a timetable for the linebacker's return.
"We address things as they arise," Tomlin said, via The Associated Press. "We felt like the procedure was necessary at this time, so we had it."
Ed Bouchette of the Pittsburgh Post-Gazette reported earlier Wednesday that Harrison was scheduled to undergo a knee operation.
We first learned of the potential of surgery Tuesday night, when Harrison's agent said a scope of the knee could be done "sooner than later." Harrison has been bothered by continued irritation behind his kneecap and has yet to practice this summer.
The surgery was scheduled to allow Harrison the opportunity to get off the physically unable to perform (PUP) list and return to the field ahead of the Steelers' Week 1 matchup against the Denver Broncos. It remains to be seen how hard Pittsburgh will push Harrison, who's 34 and entering his 10th NFL season. It's possible he could begin the regular season on the PUP list, which would sideline him for the first six weeks.
Harrison, a four-time Pro Bowl pick, has been extremely durable during his career. He missed five games because of a broken orbital socket last season, but he has played every other game since 2007. He's due to earn $5.57 million this season.
Follow Dan Hanzus on Twitter @danhanzus.