San Francisco 49ers' Mario Manningham (82) is taken off the field on a cart after suffering an injury in the second half of an NFL football game against the Seattle Seahawks, Sunday, Dec. 23, 2012, in Seattle. (AP Photo/John Froschauer)The Associated Press
Seattle Seahawks' Richard Sherman comes down with an interception ahead of San Francisco 49ers' wide receiver Randy Moss in the second half of an NFL football game, Sunday, Dec. 23, 2012, in Seattle. The Seahawks beat the 49ers 42-13. (AP Photo/John Froschauer)The Associated Press
Seattle Seahawks' Richard Sherman jumps over San Francisco 49ers' Michael Crabtree as Sherman celebrates his interception in the second half of an NFL football game, Sunday, Dec. 23, 2012, in Seattle. (AP Photo/Elaine Thompson)The Associated Press
SANTA CLARA, Calif. – 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.
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