Source: Pitt's Mendenhall doubtful for Week 1

Updated: August 17, 2012, 4:20 PM ET

ESPN.com news services

The Pittsburgh Steelers activated Rashard Mendenhall from the physically unable to perform list Friday, but a league source told ESPN NFL Insider Adam Schefter that the running back is not expected to be ready for the team's regular-season opener or possibly even in September.

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Activating Mendenhall now, the source told Schefter, is considered the next step in the player's recovery from the torn anterior cruciate ligament he suffered in the Jan. 1 regular-season finale at Cleveland. But he still is considered a ways away from being ready to play, the source said.

The Steelers had said they weren't counting on Mendenhall this season, but general manager Kevin Colbert didn't rule out a return by the running back at some point in 2012.

Entering his fifth season, Mendenhall has two 1,000-yard campaigns on his résumé and has rushed for 3,367 yards and 29 touchdowns.

Pittsburgh also activated nose tackle Casey Hampton from the PUP list on Friday.

Hampton tore his left knee ligament in the Jan. 8 playoff loss at Denver.

A five-time Pro Bowler, Hampton has spent his entire 12-year career with the Steelers, starting 146 of 157 games.

Information from ESPN NFL Insider Adam Schefter and The Associated Press was used in this report.