DOVER, Del. -- Brian Vickers remained in a Washington-area hospital on Friday as doctors worked to dissolve blood clots that had formed in his veins.

Jay Frye, vice president and general manager of Red Bull Racing, said he believed Vickers was on an "intense type dosage" of medication, and wasn't sure when the driver would be released from the hospital or when he might return to the race track. Casey Mears will fill in for Vickers during this weekend's events at Dover International Speedway.

"At this point, we're not even sure when he's going to get out of the hospital, and we had to prepare for the weekend," Frye said. "His health is our No. 1 concern right now. ... This is something that is going to affect our chances of making the Chase. But he's a long-term player with Red Bull Racing, we're a long-term player in the sport, and our main concern is his health. If this affects the Chase, it's nothing we anticipated to happen, wanted to happen, but we've got to do what we've got to do."

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They don't know right now why this happened or what caused this to happen. ... Some of the contributing factors are things we do every week, and we do it a lot. So is that a reason? I don't know. I'm not a doctor.

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-- JAY FRYE

Vickers, who qualified for the 12-man Chase last season, is currently 20th in points, and skipping one race will almost certainly scuttle his chances of appearing in the playoff again this year. Although Frye said Vickers is in good spirits and doing well, doctors nixed the idea of the driver turning one lap Sunday in an attempt to keep his Chase hopes alive.

"The rules are the rules," Frye said. "They've been the rules for a long time. We understand them. If this affects our Chase chances, which obviously it will, we'll just reset our goals for the rest of the season."

Frye added that he wasn't sure why the clots -- one of which was near Vickers' lungs -- had formed, but he didn't rule out racing as a contributing factor. Clots in veins often occur when blood flow becomes stagnant, and can be caused by something as mundane as sitting for long periods of time, which drivers certainly do in the race car. Carbon monoxide exposure can also play a role in clots that develop in the lungs.

"Brian is a very fit young man. He takes his physical conditioning very seriously," Frye said. "They don't know right now why this happened or what caused this to happen. ... Some of the contributing factors are things we do every week, and we do it a lot. So is that a reason? I don't know. I'm not a doctor. But I'm sure it all adds up somewhere in there."

Word of Vickers' condition spread quickly through the NASCAR garages.

"I hope Brian Vickers has a speedy recovery and can join us here at race track," Kyle Busch said. "It's tough what he's going through. He's probably sitting there wondering why he's not in a car."

Jimmie Johnson said he called Vickers Thursday night. "Certainly concerned for him," the four-time champion said. "I think it's so new, they're still learning and trying to figure out what's going on with him. But I spoke with him, he's in good spirits, and I certainly hope they get to the bottom of things and get him healed up and back in the race car as soon as possible."

Added Greg Biffle: "I look at it as, that could be me. I could be laying in a hospital bed somewhere missing the race, and that would be heart-wrenching for me to have that happen. Certainly anything can happen to any one of us. We're all susceptible to something happening. We just hope and pray that nothing happens to us, and we hope that Brian gets better and gets back and races with us."

Vickers was in Washington on Wednesday in anticipation of a visit the next day with a U.S. Congressman at Walter Reed Medical Center. Frye said Vickers began experiencing discomfort in his chest similar to something he had felt the day before, and contacted Dr. Jerry Petty, a Charlotte physician who works with several NASCAR drivers. Petty advised Vickers to go to an emergency room, where he was admitted. A CT scan, Frye said, found "several" clots in the driver's veins.

Frye, whose information has come from Vickers and not the driver's doctors, said he got the call around midnight Wednesday. "We have great reason for optimism that everything is going to be fine," he said.

Still, the team had a race weekend to prepare for, and did so by hiring Mears to drive the No. 83 car for this weekend, and potentially beyond. Vickers is qualified for next weekend's All-Star Race by virtue of his victory last season at Michigan, but Frye wasn't sure Friday morning if Vickers' absence would negate that entry.

"Our focus at this point is to get through the weekend and reevaluate on Monday," Frye said. "Casey has agreed to do it as long as we need him to do it, as long as we want him to do it. We'll know more next week. There's a question about the All-Star Race, are we in or are we out? We're not really clear on that. We'll try to get clarification on that today. Certainly we hope we're in, and we plan on participating in it."

It's the second relief stint this season for Mears, who was on standby for Denny Hamlin at Phoenix and Texas after the Joe Gibbs Racing driver has surgery to repair a ligament in his left knee. Mears didn't get a chance to compete in that car, but he will in the No. 83 on Sunday.

"Obviously, we want to compete, we want to compete at a high level, and we think Casey can do it," Frye said. "Casey is a young guy who has still something to prove. We expect to compete at a very high level this weekend, just as we did before this happened."

Related:
• Vickers hospitalized, will miss Dover race