Timmons took over as starter for the 2009 season following the release of Larry Foote, who asked for his release, foreseeing Timmons's future emergence as the starter and increased playing time. Timmons was slated as the Steelers' starting right inside linebacker to begin the season but missed the season opener against the Tennessee Titans. He returned the following week, making three solo tackles and two pass deflections during a 14–17 loss to the Chicago Bears. The next game, he made his first start of the season during a loss to the Bengals and finished the game with three combined tackles and a pass deflection. During Week 5, Timmons made five tackles and forced two fumbles as the Steelers routed the Cleveland Browns, 27–14. He finished the 2009 season with a total of 78 combined tackles, 7 sacks, 4 pass deflections, and 3 forced fumbles in 13 starts and 14 games.