Westbrook was knocked unconscious during Monday night's game against the Washington Redskins when struck in the back of the helmet by the knee of a tackler. His status for Sunday's game against the New York Giants is uncertain.

"When Brian Westbrook is ready to play again, we'll have him out there. Until then, we're going to be very cautious with him like we are every one of our guys that has a concussion," Eagles head athletic trainer Rick Burkholder said.

Said coach Andy Reid: "I know Brian is going to want to play. But unless Brian's tests come back to where they're in a position where he can play, then he won't do that."

Westbrook, who had a headache Wednesday, is being partially evaluated with a brain function test known as ImPACT (Immediate Post-Concussion Assessment and Cognitive Testing).

Since 2007, all NFL players have been required to take baseline tests of brain function, administered during preseason and offseason and used to help measure recovery from a concussion.

The computerized system uses a series of memory and recognition tests. A player might be shown words in succession on a screen. Then he is tested on how many he can recall. Scores after a concussion are compared to the baseline score.

"He was tested yesterday, and he'll be tested again today," said Burkholder, one of two athletic trainers who serve on the NFL's concussion committee. "… Right now, we're in that period, which is normal, for him to have a headache, and his scores aren't quite high enough yet. They will come back."

When the headache eases and the ImPACT scores are normal, there will be other evaluations.

"The next step is you take him through an exercise program. You get his heart rate up. Does that make his symptoms worse?" Burkholder said. "If it doesn't make his symptoms worse, then you go to the next step, which is to start to do some football-type drills where you get balance and footwork and change of direction. If that goes well then you return him to practice, and then if that goes well you return him to a game."

Burkholder estimated Westbrook was knocked out less than a minute. As he was lying on the field, he was attended by Burkholder and other members of the Eagles staff. Westbrook's brother, cornerback Byron Westbrook of the Redskins, stood over him.

"Immediately, once he woke up on the field, he knew everything. He knew where he was. He knew his brother was in front of him. He knew coach Reid was behind me," Burkholder said.

Burkholder said that under NFL guidelines in place since 2007, a player who loses consciousness cannot return to play in that game. "As soon as we got up to walk, I said, 'Hey, listen now, I'm not going to you play tonight because you lost consciousness,' and he said, 'I totally understand,' " Burkholder said.

Burkholder said Westbrook could not recall the play on which he was hit.

"He has a very short interval between breaking the huddle and the play that he doesn't remember. That's called retro-grade amnesia. It's not a big indicator for us when we look at recovery," Burkholder said. "… The amnesia that we worry about is that he can't remember things that happened after he got hit. He has none of that. He remembers waking up. He actually remembers that he was dreaming."

Burkholder said Westbrook will we watched over the coming days for other symptoms, such as whether he becomes irritable or depressed.

For now, the key step is to get past the headache.

"The only symptom he has right now really is the headache, and that's enough for me," Burkholder said. "It doesn't matter if he has seven symptoms or one symptom, I'm not going to let him progress to the next level until he gets rid of the headache."

Enlarge By Molly Riley, Reuters The Eagles' Brian Westbrook, center, is led off the field after suffering a concussion in the first quarter of Monday night's game against the Redskins.