Westbrook was playing his first game after sitting out two because of a concussion suffered Oct. 26. He was injured in the third quarter Sunday on a screen play in which he was caught between a block by Eagles receiver Jason Avant and Chargers safety Eric Weddle.
Eagles coach Andy Reid said the team will take precautions with Westbrook and it's too early to tell when Westbrook will return, if at all.
"Football right now for Brian Westbrook is not the important thing," Reid said Monday. "It's making sure that we get him analyzed, tested and taken care of and then we'll go from there. Not that we didn't do that before.
"We took every precautionary measure that we could before and it happened again. Obviously we're going to check with experts and make sure that we listen to them like we did before. The No. 1 thing is Brian's health. You can put football aside and make sure that he's taken care of here."
Westbrook wasn't available to reporters on Monday. His agent, Todd France, didn't immediately return a phone message.
The 30-year-old Westbrook sustained his first career concussion when he hit his head on a defender's knee during a Monday night win at Washington last month. Westbrook briefly lost consciousness but walked off the field under his own power.
He sat out Philadelphia's victory against the New York Giants on Nov. 1 and was cleared to play against Dallas last week, but was held out for precautionary reasons after experiencing headaches. Westbrook had no problems leading up to the game against the Chargers.
"We left it up to the doctors," Reid said. "There's a chance he could have played the week before and we held him out of that one according to tests and symptoms. He was symptom-free and tests came back normal and so on, so I did what the experts said. They felt comfortable with it and we went with it."
Reid wasn't sure if a second concussion is more serious. Westbrook didn't lose consciousness on this one.
"I've heard a couple different things on that," he said. "Obviously it's not a good thing for a second one to happen. I don't know the medical terms of it. I've heard them determine it by if it was a mild hit as compared to a severe hit. It wasn't a mild hit I would say."
The eight-year veteran has been limited this season by ankle and knee injuries and the concussions. Westbrook has carried the ball 47 times for 225 yards, an average of 4.8 yards per carry, and has scored one touchdown. He has also caught 19 passes for 156 yards and a TD.
Before last season, Westbrook signed a three-year contract worth $21 million, including $13 million guaranteed the first two years. The Eagles have the option of not renewing his contract for 2010.