ASHBURN -- The first step is finding out what's wrong, which is what doctors were trying to do Thursday. The next is figuring out whether the Redskins must survive a game without London Fletcher.

The Redskins' veteran linebacker and defensive captain did not practice Thursday because he was still being examined by neurologists -- he had been with them for at least six hours by late afternoon. Coach Mike Shanahan said they had hoped to hear by Thursday night the results of those tests. He said he's not sure whether Fletcher suffered a concussion at some point, which the tests would reveal.

Fletcher owns the NFL's longest active consecutive games played streak at 231. In fact, he has never missed a game in his NFL career.

» Receiver Pierre Garcon said he does not consider surgery an option on his ailing toe, but he also knows it's a possibility if it doesn't improve in the next few weeks. Garcon has not practiced this week and is unlikely to play at Pittsburgh on Sunday and perhaps not the following week vs. Carolina. Garcon has a lateral ligament tear under the second toe on his right foot. He has played in only three games because of the injury. Garcon said he first hurt his toe this summer but figured it was just a "football injury" and thought it would get better. He hurt it in the opener at New Orleans. "It was overuse," he said. "That's the best term. I felt it early in the preseason and I just kept playing. I'm kind of stubborn. [I thought], 'It's just a toe injury, so it'll be all right.' In New Orleans I felt it pop, and that's when things are serious, when you feel a pop. I don't want to be on the sidelines. It's frustrating, but you just have to think what's best for it and what's best for the future. This is long term; you don't want to make it worse just for one season."
» Safety Brandon Meriweather, like Garcon, did not practice Thursday. Meriweather's knee was sore after working some Wednesday.

"If he's able to go, you know he'll go," Shanahan said. "I'm sure he's scared, too. Anytime you deal with a balance issue it's something that's out of your control. London's a smart guy. He wants to play, but at the same time he understands if there's something wrong with your balance it's a tough situation to be in."

Fletcher's status would have been uncertain this week anyway because of a slight hamstring pull that caused him to miss the fourth quarter vs. New York on Sunday. Until he's cleared to run, Fletcher can't test his hamstring.

If Fletcher can't play, the Redskins would lose arguably the players' most trusted defensive voice in the building. Fletcher leads the Redskins with 59 tackles, but it's his ability to anticipate and put players in the right spot that would be tough to replace. He's also their best cover linebacker against tight ends; Pittsburgh tight end Heath Miller has 31 catches for 290 yards and five touchdowns.

Lorenzo Alexander, in his first full season as inside linebacker, and rookie Keenan Robinson would replace Fletcher.

"What you lose from London is the leadership role, the passion and energy he brings to the game, much like Ray Lewis," Alexander said. "You can't match what he brings experience-wise. ... I know the defense pretty well. The biggest thing is knowing what the opposition is going to do. ... He does it so well that guys are able to jump things and play with leverage depending on what the call is.

"But am I capable of playing and winning games for us as well? Yes. Is Keenan able to do that? Yes."

Alexander has played defensive line, outside linebacker and now inside. He likes where he's at now. He said when he replaced Fletcher on Sunday, there weren't any calls that he missed or plays he didn't recognize by New York. Alexander is adept at rushing inside; dropping into coverage is not his strength just yet.

"It's most natural for me," Alexander said. "I'm not a natural pass rusher off the edge. The [inside] linebacker is probably the most comparable to what I do on special teams, being able to roam, fill, spill blocks, hit people. That's what I'm most naturally gifted at."

Robinson covered in college and is considered a fast linebacker. The Redskins say he's smart, too.

"I feel I'm learning pretty fast," Robinson said. "They had high expectations for me. I'm learning all the [linebacker] positions, and I've come along faster than most other guys."

It's possible that he'll need to come even further along this week, making up for not having Fletcher.

"That would be a different feeling," defensive coordinator Jim Haslett said. "But I feel good about the guys we're playing."