SANTA CLARA — Tight end Vernon Davis, the 49ers' second-leading receiver this season, left Sunday's game in the second quarter and was ruled out after being diagnosed with a concussion.

Davis took himself out after dropping a second-quarter pass near the Panthers' 5-yard line and landing hard on his head when tackled by safety Mike Mitchell.

Davis nearly caught Colin Kaepernick's second-down pass before it got knocked out by linebacker Thomas Davis, and a Panthers replay challenge only confirmed the officials' ruling of an incompletion.

Davis last sustained a concussion Dec. 23 at Seattle, and although he did not return to that game, he did play the following week.

The 49ers played the second half with only one healthy tight end, Vance McDonald. Third-stringer Garrett Celek was ruled out with a hamstring injury in the first quarter.

The 49ers' took a 9-7 lead into halftime against the Panthers, using three field goals from Phil Dawson to take a 9-0 lead. DeAngelo Williams spoiled the 49ers' shutout bid when he ran 37 yards for a touchdown, avoiding potential tackles from defensive backs Carlos Rogers, Tarell Brown and Eric Reid.

Dawson's third field goal was set up by Tramaine Brock's fourth interception of the season.

Aldon Smith, in his return from a five-game hiatus, played only three snaps in the first half. He helped pressure Newton into a third-down incompletion upon entering the game with 12:48 left until halftime.

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