Regan Smith has been handed a full season in the 2013 NASCAR Nationwide Series, after signing a deal to race for the JR Motorsports team owned and operated by Cup driver Dale Earnhardt Jr.

Smith has just finished a two-week stint sitting in for Earnhardt in the #88 Hendrick Motorsports Cup car, after the announcement that Earnhardt had been sidelined from races in Charlotte and Kansas following a double concussion.

Smith had previously been racing for the Furniture Row Racing team in the #78 car, but left the squad after Talladega following the announcement that the team had signed Kurt Busch to take the ride in 2013. That leaves Smith without a confirmed Sprint Cup Series drive next season.

Smith had planned to see out the rest of the current season as a stand-in driver at Phoenix Racing in a straight swap with Busch, but was then handed the two-race stand-in opportunity at Hendrick instead and opted to take that. Phoenix brought in AJ Allmendinger to drive their #51 car, and announced on Tuesday that Allmendinger will remain in the car for the next two races at Martinsville and Texas.

Smith said earlier this week that he completely understood why Phoenix Racing owner James Finch had needed to make the call when he did, admitting that that team "just had to be able to commit to something" and hadn't been able to wait around until Earnhardt's medical status was confirmed one way or another.

"For a time period there, we were just having to wait and see a little bit to see how things went at his test," explained Smith. "I think everybody was anticipating things were fine and the test was going to go fine, but there was that little bit of wait-and-see moment, and [Phoenix Racing] had to be able to work toward what they were doing at Martinsville."

However, the team has now also said that they will bring back Smith to race for them in the final two events of the 2012 season at Phoenix, Arizona and at Homestead, Miami in November. That means that it's still possible that Smith will find a 2013 Cup ride with Phoenix Racing to go along with his confirmed Nationwide Series outings at JR Motorsport.

Whatever his Cup future, Smith said that he was delighted to be heading back to the Nationwide championship next year at the wheel of the #5 JR Motorsports car. He last competed in the series in 2007.

"This is an extremely good opportunity for me," said Smith of the deal announced on Wednesday. "Dale Jr. and I first started talking about this several years ago, but the timing never matched up to where we could make it happen. Now it's time.

"This gives me a chance to contend for race wins and championships," he added. "That's why we do all that we do. I love the Cup series, I love the grind of it - with that being said, this definitely is an opportunity I couldn't pass up."

As a stand-in for Earnhardt over the last two weeks, Smith seems to have done enough to impress his future team boss. He suffered an engine failure in the #88 in his first outing, but went on to claim seventh place in Sunday's hazardous race at Kansas.

"Regan has always impressed me," said Earnhardt. "He gets the most of his car, no matter what he's driving or who he's driving for.

"He takes care of his cars and gets good finishes. With his experience and ability, we feel he can excel in our equipment. He has a super personality, and his ability to work with everyone here at JR Motorsports and Hendrick Motorsports will be important in getting us back to the winner's circle."

JR Motorsport currently fields a two-car full-time line-up consisting of Danica Patrick and Cole Whitt, and will add a third car for Smith at the season finale at Homestead to welcome him into the fold.

Patrick is due to switch to full-time Cup racing with Stewart-Haas in 2013, and the team is still seeing whether it can fund a second car for Whitt who this year has driven the #88 car in the Nationwide Series. However, the team have said that if Whitt is confirmed for another season with them he'll be switched to the squad's #7 car in order that Earnhardt can participate part-time in the series at the wheel of the iconic #88, with which he is most famously associated.

"We feel it is important for our sponsors, our fans, and even Dale to keep his Nationwide Series number consistent with his Cup number," said Kelly Earnhardt Miller, Dale's sister and a co-owner of JR Motorsports. "His brand is associated with the #88. That's what makes him distinguishable on the race track, so it's only natural that he drives the #88 all the time.

"To do that, we are making our #5 Chevrolet our full-time entry [with Regan]," she added. "We hope to have Cole in the #7 full-time in 2013, and we are working hard on securing sponsorship for that."