San Francisco, CA -- (Sports Network) - Eldra Buckley's touchdown catch with 29 seconds to play lifted the San Diego Chargers to a 20-17 win over the San Francisco 49ers in the preseason finale for both squads.

With time winding down in the fourth quarter, Charlie Whitehurst found Buckley in the end zone from two yards out to give the Chargers a 20-17 lead with 29 seconds left as the team grabbed the win.

Whitehurst went 15-for-32 with 144 yards while Mike Tolbert had a touchdown catch on three receptions for 32 yards for the Chargers (3-1), who open up their regular season at home against Carolina on September 7.

Alex Smith, who lost the starting quarterback job to J.T. O'Sullivan, went 12- for-17 with 146 yards, one touchdown and two interceptions for the 49ers (2-2), who open up their season at home against Arizona on September 7.

As was expected, most of the regular starters for both teams sat out the game.

San Diego took the lead on its first possession of the game as Billy Volek capped a 12-play, 79-yard drive with a six-yard toss to Tolbert for a 7-0 lead with 7:29 left in the first.

The 49ers answered on their ensuing possession on a 52-yard field goal from Joe Nedney to make it a 7-3 contest.

A 49-yard Nate Kaeding field goal gave the Chargers their seven-point lead back with under six minutes to play in the first half, but Delanie Walker took the kickoff back 101 yards to tie the game.

Kaeding connected on another field goal, this one from 35 yards out, to give the Chargers a 13-10 lead heading into the locker room.

The 49ers started the second half with the ball and Smith led them down the field to a 17-13 lead on a 22-yard touchdown pass to Billy Bajema.