SAN FRANCISCO — Even against his hometown team's third-stringers and scrubs, Alex Smith demonstrated why he's no longer the San Francisco 49ers' starting quarterback.

Smith passed for 146 yards but also threw two terrible interceptions, and San Diego's Eldra Buckley made a one-armed diving catch on a 2-yard touchdown pass with 29 seconds left in the Chargers' 20-17 exhibition victory over the 49ers last night.

"All good quarterbacks throw picks, and they score touchdowns, and the really good ones are a point better than they are bad," said 49ers coach Mike Nolan. "Alex has to learn that, and the only way he's going to learn it is by what he did today."

Just four weeks ago, Smith never would have expected to be playing three quarters in the season's most meaningless game. But the former No. 1 overall draft pick gradually lost his job to J.T. O'Sullivan, the journeyman quarterback who will start for the 49ers (2-2) in next week's home opener against Arizona.

Given Smith's 37.5 passer rating in the first half against the Chargers (3-1), he didn't even look like a sure bet for the backup job until Shaun Hill also struggled in the second half.

Charlie Whitehurst passed for 144 yards and Malcom Floyd had six catches for 68 yards for the Chargers.

Hobbled linebacker Shawne Merriman was in a San Diego uniform during warmups, but he joined LaDainian Tomlinson, Philip Rivers, Antonio Gates, Chris Chambers and Jamal Williams on the sideline when the game began.

Former University of Hawai'i linebacker Jeff Ulbrich had four total tackles, while Radford High alum and ex-UH standout Ashley Lelie, a receiver, didn't record any stats.

BRONCOS 28, CARDINALS 14

GLENDALE, Ariz. — Matt Leinart gained a measure of redemption in Arizona's preseason finale.

Leinart relieved starter Kurt Warner and directed the Cardinals to two touchdowns in the loss to Denver (2-2)

Leinart was 10 of 14 for 177 yards and a score.

Although the performance came against Denver's reserves, it was a welcome reversal for Leinart after an awful outing last week at Oakland put his status as starter in doubt.

Darrell Hackney threw for 208 yards, including an 87-yarder to Keary Colbert that put the Broncos up 21-14 with 8:51 remaining.

Kahuku alum Aaron Francisco and former UH standout Travis LaBoy each had one tackle for Arizona (2-2).

SEAHAWKS 23, RAIDERS 16

SEATTLE — T.J. Duckett showed he may be more than just the short-yardage back coach Mike Holmgren thinks he is by running for 71 yards and two touchdowns for Seattle (3-1).

Seattle's Seneca Wallace was 21 of 30 for 225 yards.

Oakland's JaMarcus Russell, who will start the Sept. 8 opener against Denver, was in uniform, but didn't play. Andrew Walter was 16 of 24 for 162 yards for Oakland (1-3).

Seattle receiver Ben Obomanu broke his clavicle early the game.