San Francisco 49ers defensive lineman Ronald Blair chased after and took down Seattle Seahawks quarterback Russell Wilson in the fourth quarter and did not immediately get back up.

Blair needed some assistance getting off the field while avoiding putting weight on his right leg, was examined in the medical tent, and then carted to the 49ers locker room for further evaluation.

Update: Blair has been ruled "out" with a knee injury.

San Francisco currently trails Seattle by a score of 24-21 late in the fourth quarter.

The other players who have left the game are wide receiver Emmanuel Sanders (ribs), defensive tackle D.J. Jones (groin), linebacker Azeez Al-Shaair (concussion), and running back Matt Breida (ankle).

Center Weston Richburg, defensive lineman Solomon Thomas, and cornerback K'Waun Williams also left the game but eventually returned.