SAN DIEGO - The injuries just keep on coming.

Before the Eagles even took the field yesterday at Qualcomm Stadium, they learned that left tackle Jason Peters, their top off-season acquisition, would not play because of a sprained ankle.

By the time they were finished with their 31-23 loss to the San Diego Chargers, two more prominent players were confined to the sideline.

Cornerback Sheldon Brown left after one series in the third quarter because of a hamstring injury he suffered during a first-quarter punt, and running back Brian Westbrook left after suffering his second concussion in as many games during the third quarter.

"I'm going to have an MRI in the morning," Brown said. "It's one of those things that's tough because that was the first time I ever had to leave a game."

Brown said he had tried to play through his injury at the start of the second half, but realized after one series that he would not be able to do it.

"I need to be accountable for this team over the long haul," he said. "I wanted to be selfish and stay out there, but if I get hurt in this one game I'm letting all these guys down."

It's his first-ever hamstring injury, Brown said.

With Brown being treated in the locker room during the second half, the Eagles had to use Dimitri Patterson as the No. 2 cornerback and newly signed Ramzee Robinson as No. 3 because Ellis Hobbs had been lost to a season-ending neck injury and Joselio Hanson to a four-game suspension last week.

Patterson was asked to cover Chargers tight end Antonio Gates several times and struggled.

On a third-and-6 play on San Diego's final drive, quarterback Philip Rivers found Gates on a slant over the middle for a 17-yard gain that allowed San Diego to take valuable time off the clock while moving into Eagles territory. The Chargers would settle for a field goal, but it gave them an eight-point lead with just 33 seconds remaining.

"It was one of those days where I was just trying to get into a rhythm," Patterson said. "When you're coming back, you never know what to expect, and you're going to get in situations where you have to battle through them. That last drive with about five minutes left, there were a couple of third-down conversions where we didn't execute."

Veteran cornerback Asante Samuel blew coverage on an 18-yard catch by Legedu Naanee on a third-and-2 play with less than three minutes remaining. Samuel also lost track of Naanee on a 20-yard touchdown that allowed the Chargers to build a 28-9 lead with 1:13 left in the third quarter.

Westbrook's day also ended after one series in the third quarter. The running back caught a 9-yard screen pass from Donovan McNabb and was drilled by linebacker Stephen Cooper and safety Steve Gregory.

Westbrook did not return after that play, and it was announced in the fourth quarter that he had suffered his second concussion in a month after sitting out the Eagles' previous two games.

Coach Andy Reid wasn't prepared to say Westbrook's concussion threatened his career.

"I don't know," Reid said. "It's too early right now."

As for Peters, he hadn't practiced the entire week after his right ankle was sprained against Dallas, but he kept insisting he was going to play against the Chargers. It was decided before game time, however, that he would not.

Peters' absence forced the Eagles to move Todd Herremans to left tackle and Nick Cole from right guard to left guard. Stacy Andrews got the start at right guard, his first since the season opener in Carolina. Herremans hadn't started at left tackle since his rookie season in 2005, when he started four games in place of Tra Thomas.

The makeshift line did a solid job protecting McNabb, who was sacked just twice while throwing 55 passes.

Jackson hurting

It was announced during the game that receiver DeSean Jackson had injured an ankle, but Reid did not mention the injury afterward, and Jackson played the entire game. The Eagles did opt to use Jeremy Maclin on two punt returns in the middle of the game. He fielded and returned only one, for 7 yards.

Maclin also returned the Chargers' first four kickoffs, but appeared ill-equipped for the job, averaging just 18 yards.

Rookie Macho Harris took over that role on the final two kickoffs and averaged 28.5 yards. Harris could keep that role even after fellow safety Quintin Demps returns from an ankle injury. Demps said he thinks he'll return Sunday at Chicago.

Vick's moment

The Eagles used Michael Vick for just one play, and it should have worked for a big gain. Jackson probably should have caught the throw from Vick, but the pass was behind him.

Contact staff writer Bob Brookover at 215-854-2577 or bbrookover@phillynews.com.