(Renton, WA)  --  Seattle Seahawks head coach Pete Carroll says there's no timetable for the return of injured running back Marshawn Lynch.  Lynch is rehabbing from abdominal surgery, and his replacement, rookie Thomas Rawls, is out for the rest of the season with an ankle injury.  Carroll says the team has signed running back Bryce Brown, who spent most of last month with the Seahawks, after signing as a free agent in late October.  Brown is expected to compete with DuJuan Harris and Derrick Coleman for the starting running back spot, and veteran Fred Jackson will continue his role as third-down back.