Graham, who suffered a right knee injury during the fourth quarter, will not return to Sunday's game against the Steelers, Liz Mathews of 710 ESPN Seattle reports.
The injury appeared serious, with Graham staying down on the field for a few minutes and then leaving with an air cast over his right leg. Owners will want to wait for further updates before taking action, but there is some chance Graham won't play again this season, in which case Luke Willson would take over as Seattle's top tight end.