CONCORD, N.C. -- Regan Smith's first outing as the substitute for NASCAR's most popular driver was a short one.
Sixty-one laps into Saturday night's Sprint Cup race at Charlotte Motor Speedway, the engine blew in the No. 88 car that Smith inherited from Dale Earnhardt Jr., who has been ruled out for at least two weeks to recover from symptoms of a concussion.
Smith was having a decent night, running in the top 15 after starting 26th. The cause of the engine failure was not known.
"The important part is that we had a really fast race car," Smith said. "We had a good first adjustment there, went just a little too far with it and got a little too free. Needed one more stop, and I think we would have had it dialed in."
Earnhardt was sidelined by NASCAR's chief physician, Dr. Jerry Petty, on Thursday after suffering multiple concussions in the past six weeks.
The first concussion occurred during an Aug. 29 test at Kansas Speedway, but Earnhardt did not report it. He went to Dr. Petty after experiencing headaches associated with a concussion following Sunday's last-lap crash at Talladega.
Smith was scheduled to drive the No. 51 for Phoenix Racing after being replaced by Kurt Busch in the No. 78 at Furniture Row Racing. He got the call from Hendrick Motorsports on Thursday morning to replace Earnhardt.
"It's disappointing," Smith said. "It's a good team, it's a good car and everybody at Hendrick Motorsports does a great job. I'm looking forward to next week.
"We get three days to test when we get there to Kansas and we will see if we can get the AMP Energy/National Guard Chevrolet up front there. I feel confident we will have the same speed we had here."
Earnhardt basically was out of the championship hunt in 11th place, 51 points out of first. He did not come to the track Saturday, saying Thursday he didn't want to be a distraction to his team.
Smith is hoping his time in the No. 88 will lead to another ride in 2013. He is a top candidate to drive in the Nationwide Series for JR Motorsports.