SANTA CLARA, Calif. (AP) — Mario Manningham limped through the locker room on crutches, holding a towel around his waist while trying to keep his head high and sport a smile.

That’s not an easy thing to do for the San Francisco 49ers right now.

Manningham is out of the season with left knee injury after he getting tackled low by Leroy Hill and fumbling in the third quarter of San Francisco’s 42-13 loss at Seattle. It’s another blow to an increasingly thinning wide receiver corps.

Tight end Vernon Davis was not expected to practice later in the day. He still must clear the league’s NFL concussion protocol after taking a huge hit from Seattle’s Kam Chancellor.

Kyle Williams (left knee) already is lost for the season.

The 49ers (10-4-1) will rely more than ever on Randy Moss and first-round pick A.J. Jenkins to support top threat Michael Crabtree.