SANTA CLARA, Calif. (AP) -- Philip Rivers never looks too much into preseason success or lack of it, though he certainly appreciates finding a nice August rhythm to carry into the regular season.
San Diego's quarterback appears to have found that, completing his first five passes and 9 of 10 overall in the Chargers' 21-7 loss to the San Francisco 49ers on Sunday.
"We got first downs, finished with a touchdown and you like to get in that flow," he said. "The other two games we only got one series, so getting to go through series, going back out there over and over is how you get into that flow, which is important this close to the opener."
An illegal block nullified Rivers' 25-yard touchdown pass to Ryan Mathews in the final minute of the first quarter, but Rivers connected on a 10-yard TD pass to Antonio Gates on the next play.
The Chargers outgained San Francisco 121-17 in the first quarter -- but not without a cost.
Defensive tackle Kwame Geathers went down with a knee injury at the 7:09 mark in the first quarter, while center Nick Hardwick suffered a first-half neck injury.
"There are still some things we need to clean up because we have the philosophy you are only as good as your weakest link," Gates said.
There were tens of thousands of empty seats hours after an overnight 6.0-magnitude earthquake struck in the Northern California wine country near Napa. The quake affected some public transportation options to the new $1.2 billion stadium, which was sold out last Sunday.
The patchy field is still hardly ideal, with visible lines where new sod was placed Friday after the initial turf failed to hold.
Phil Dawson kicked a 39-yard field goal at the 9:27 mark of the second quarter, ending an eight-quarter scoreless drought for the 49ers as they doubled their preseason total. Dawson added another from 28 yards a week after missing twice.
Dawson didn't get on the field until Sunday morning.
"I'm just amazed that was playable," Dawson said. "It was an improvement, so hats off to those guys who worked so hard to get it in. Fortunately I missed two last week so my focus was solely on trying to make a field goal, so I didn't have enough room in my brain to worry about the field."
49ers backup quarterback Blaine Gabbert threw a 6-yard touchdown pass to Vance McDonald late in the first half for the 49ers' first TD of the preseason. That capped a drive in which Gabbert went 5 for 6.
Colin Kaepernick was 6 of 12 for 59 yards.
With Rivers' outing and Peyton Manning's 12-of-14 performance in a 34-0 rout last Sunday, the new-look 49ers secondary allowed the past two starting quarterbacks to complete 21 of 24 passes for 187 yards and passer ratings of 120 or better.
San Diego's swarming pass rush made things tough on Kaepernick, who was hit hard four times in three first-quarter series.
Kaepernick lost a fumble when he got stripped and pounded by Corey Liuget, who beat left guard Mike Iupati. But the Chargers failed to score when Ryan Mathews was stuffed on fourth-and-1 from the 5 by Michael Wilhoite.
"We were motivated as a team and as a defense more than anything," Liuget said. "That was one of the best lines we'll see, and a very potent offense, too. To come in and play the way that we did defensively, I think was excellent."
Kaepernick was hit again on his next pass attempt, then a fourth time during his third series.
The Chargers have lost the past five preseason meetings between the teams, who have faced off in the exhibition schedule every year since 1987. Neither showed much given they play here again in Week 16 on Dec. 20.
San Francisco's Glenn Winston ran for a 27-yard touchdown in the fourth quarter against a Chargers defense that allowed five TDs rushing in a 41-14 loss to the Super Bowl champion Seattle Seahawks.
"We had something to prove after last week. We really put a focus on stopping the run, and I thought we did a good job," linebacker Donald Butler said. "It's good that when you put a focus on something, that you're able to go out there and do it."
