By STEVE REED
AP Sports Writer
CONCORD, N.C. (AP) - Dale Earnhardt Jr.'s replacement made an early exit Saturday night in the NASCAR Sprint Cup race at Charlotte Motor Speedway.
Regan Smith, filling in for the concussed Earnhardt for at least two races, went to the garage with a blown engine early in the race.
Smith was running extremely well early having moved up from 26th to 10th before smoke began borrowing from his car. He said he wasn't sure exactly what went wrong with the car, but immediately parked it behind the wall for the night.
"It's disappointing and it's a shame," Smith said.
Smith also will drive Earnhardt's No. 88 Chevrolet next week at Kansas.
"I'm getting more and more comfortable in these cars," Smith said.
KENSETH TAKES SPIN EARLY: Matt Kenseth couldn't carry over his momentum from last week's win at Talladega, spinning out and hitting the wall after his left rear tire went down minutes into the race.
Although Kenseth was able to continue, he fell a lap down and brought out the first caution. On the ensuing restart, defending NASCAR champion Tony Stewart ran into the back bumper of points leader Brad Keselowski.
Kenseth came into the Chase last in the 12-driver field, 62 points behind Keselowski.
GORDON ON CONCUSSIONS: Earnhardt Jr. was praised by his competitors for having the guts to seek medical attention that led to him being sidelined Saturday night at Charlotte Motor Speedway.
But, at least one driver wasn't sure he'd do the same with a championship on the line.
"Honestly, I hate to say this, but no, I wouldn't," four-time champion Jeff Gordon said. "If I have a shot at the championship, there's two races to go, my head is hurting, and I just came through a wreck, and I am feeling signs of it, but I'm still leading the points, or second in the points, I'm not going to say anything. I'm sorry.
"You know, that's the competitor in me, and probably many other guys. And, that's to a fault. That's not the way it should be. It's something that most of us, I think, would do. I think that's what gets a lot of us in trouble."
Earnhardt was diagnosed this week with two concussions sustained over a six-week span. He was first injured in an Aug. 29 crash during a tire test at Kansas, but he didn't seek an evaluation for what he knew was a concussion after he left the track.
Then, he had a lingering headache following Sunday's 25-car accident at Talladega.
2013 CAR: NASCAR asked three drivers at this week's tire test at Texas to run in a pack so officials could get a look at the 2013 car in traffic.
Nobody loved what they saw.
"We feel like we've got a little more work to do with the car and the mechanical grip," said Greg Biffle, who ran some laps in traffic with Kyle Busch and Paul Menard.
NASCAR has been working all year on a plan to improve the racing, and the launch of the 2013 car is supposed to create a clean slate for changes. The hope is to make passing easier, but Biffle didn't believe that was the case Wednesday at Texas.
"They seem to be pretty aero-tight, similar to our cars now, maybe a tick more, but we don't know that because we didn't have any 2012 cars there to compare that to," he said. "So it would be unfair to say they're worse than the 2012 car right now before we make additional changes to them. They were pretty tight behind each other."
But there's more testing planned, and Goodyear is working in conjunction with NASCAR to develop a tire that can improve the overall on-track product.
"I think they've got a lot of ideas to try," Biffle said. "Goodyear is working hard at trying to come up with a tire that complements that so we can get the racing a little more side-by-side."
DRIVE FOR DIVERSITY: NASCAR's Drive for Diversity Combine is scheduled for next week at Langley Speedway in Hampton, Va.
A group of 17 drivers representing 12 states, Canada and Mexico have been selected to participate in the combine, which determines the NASCAR Driver for Diversity (D4D) program drivers for the 2013 season. The drivers compete for the Rev Racing team.
This year's combine will be a three-day driver evaluation of on-track performance, marketing and media aptitude and physical fitness. Langley, a 0.4-mile asphalt oval, is hosting the event for the second consecutive year.