The move will free up approximately $5 million in salary-cap space for the Steelers. In 2011, Timmons signed a six-year, $50 million deal.
This is the latest in a series of moves, as the Steelers try to get under the 2013 cap.
The team also has met with representatives for quarterback Ben Roethlisberger to work on renegotiating the two-time Super Bowl champion's contract. Roethlisberger is scheduled to carry a prohibitive cap figure of $19.595 million in 2013.
An agreement between Roethlisberger and the Steelers might come by the end of the week.