Steelers trade Mahan back to Bucs who ship Buenning to Bears

A year after signing Sean Mahan to help the interior of their offensive line, the Steelers decided to go a different direction by trading him back to the Tampa Bay Buccaneers for a seventh-round pick.

Mahan, 6-foot-3, 301 pounds, left the Bucs to sign a five-year, $17 million contract last season and started the season for Pittsburgh at center. Because the AFC North is loaded with big nose tackles in 3-4 schemes, Mahan struggled even though he started 16 games.

Mahan will help the Bucs at either guard or center. Guard Davin Joseph is out most of September because of a broken foot. Mahan will also return to a conference in which 13 of the teams play 4-3 schemes, which is much easier for a lighter interior offensive lineman.

The Bucs have not asked Mahan to re-adjust his salary. In Pittsburgh, Mahan lost his starting job to Justin Hartwig.

The Buccaneers then turned around and shipped guard Dan Buenning to the Bears for an undisclosed 2009 draft choice, believed to be a sixth -- according to a source.

A fourth-round pick in 2005, Buenning started 16 games as a rookie, but his playing time diminished over the next two seasons. He started seven games in 2006 and didn't start or play a game last season.

The 6-foot-3, 320-pound Buenning is expected to help the team's depth at guard. Starting left guard Terrence Metcalf missed most of the preseason because of knee surgery. Josh Beekman has been filling in at left guard.

Senior writer John Clayton covers the NFL for ESPN.com.