He played college football for the Ohio State Buckeyes,[1] and was selected by the Cowboys in the first round of the 2006 NFL draft.

In 2003, Carpenter started three contests at strongside linebacker, totaling 37 tackles (24 solos), 4.5 sacks, 6.5 stops for losses and a pair of forced fumbles.

As a senior in 2005, Carpenter started first eleven games of the 2005 season, finishing fifth on the squad with 49 tackles and second on the team with eight sacks and 10.5 stops for losses, earning second-team All-Big Ten Conference honors.

His best game with the Cowboys came in a 2006 playoff loss to the Seattle Seahawks, where he started at outside linebacker and recorded five tackles and three deflected passes.

In the fourth episode of the 2008 Hard Knocks series, Carpenter was continuously beaten in a pads and shorts practice by right tackle Marc Colombo.

On September 6, 2010, the Miami Dolphins signed Carpenter as a free agent, reuniting him with Bill Parcells, who drafted him with the Dallas Cowboys.

[12] Following the signings of Justin Durant and Stephen Tulloch, it looked like Carpenter would test free agency again, but he was re-signed after the injury and release of Zack Follett.

[13] On October 2, 2011, Carpenter had six tackles, a pass deflected and made the play of the game, returning an interception for a touchdown, which sparked a second half come-from-behind victory against his former team, the Dallas Cowboys.

The 24-point collapse was Dallas' largest blown lead in team history and eventually cost them a chance to qualify for the post-season.

He is jokingly referred to as "General Bob", due to his "rallying of the troops" which led to the Big Ten Conference reversing their decision to suspend the 2020 season.