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AJ Allmendinger returned from an early morning workout to find a slew of missed calls and text messages on his phone.

"I thought this is either something good, or something really, really bad," Allmendinger said.

It was really good news for Allmendinger.

Phoenix Racing has grabbed Allmendinger to drive the No. 51 Chevrolet this weekend as part of the domino effect from Dale Earnhardt Jr.'s concussion. It's the first time Allmendinger has been in a car since his July 7 suspension for failing a random drug test, and comes a week after he spoke briefly with Phoenix owner James Finch at Talladega in Allmendinger's first trip to a NASCAR race.

"I talked to Finch for about three minutes this morning," Allmendinger said Thursday. "He started to tell me what the deal was and I was like, 'Man, it's all good. I'll come drive this weekend, and if you like me, you like me. And if not, it's OK.' It's all about taking it as it comes right now."

Kurt Busch had been driving for Phoenix this season, but left the team this week to get an early start on next year's partnership with Furniture Row Racing. That displaced Regan Smith in the Furniture Row ride, and Finch planned on using Smith for at least Saturday night's race at Charlotte Motor Speedway.

Then a doctor decided Earnhardt should not race the next two weeks because of a concussion he suffered in the 25-car wreck at Talladega on Sunday. Team owner Rick Hendrick called Finch late Wednesday and asked for Smith, who is a candidate to run for the Nationwide championship next season at JR Motorsports.

Smith received a text message at 7 a.m. on Thursday morning from Earnhardt crew chief Steve Letarte, who informed Smith he'd be driving the car of NASCAR's most popular driver the next two weekends.

Once he accepted, Phoenix Racing scrambled to find Allmendinger.

It's the break Allmendinger has been waiting for. He has said he tested positive for Adderall, a prescription drug typically used to treat attention deficit disorder, and completed NASCAR's "Road to Recovery" program. The series reinstated him last month, but he was dropped by Penske Racing after his backup "B'' urine sample also failed a drug test.

Still looking for work for 2013, Allmendinger wasn't sure if anyone would take another chance on him.

He is not sure how rusty he will be this weekend.

"I've just got to get comfortable," Allmendinger said. "This is the longest I haven't driven a race car in at least six years. In the offseason, I'm always driving a Rolex car and our (NASCAR) offseason is only two months, anyway. So I'm a little nervous, trying to get back into the flow of things.

"I don't expect to set the world on fire. I'm just trying to get used to it again, progress through the weekend, limit my mistakes, finish all 500 miles and wherever that puts us, it puts us."

The first issue the team encountered was a big one — the car had been fitted Monday for Smith, and Allmendinger couldn't reach the pedals when he got inside the cockpit on Thursday. It forced the lean Phoenix crew to scramble to move the throttle and make the adjustments needed to get Allmendinger on the track in time for first practice.

Allmendinger, who also had to use tape to shorten his Phoenix firesuit, wasn't complaining.

"In a situation like this, beggars can't be choosers," he said.

Meanwhile, Smith hustled to Hendrick Motorsports to get fitted for his second car in a week. He was in Phoenix firesuit, but wearing a hat bearing the logo of Earnhardt's sponsor.

"The past four weeks have been about as up and down as any four weeks in my life," said Smith, who learned in the last month he was being let go by Furniture Row and then he was replaced before the end of the season.

"I just want to do these guys proud and run as good as we can this weekend with this car," he said. "They're the same goals this team has every weekend: We want to go out there and try win the pole and try to win the race and try to be the fastest car in every practice. That's not going to change this weekend."