CONCORD, N.C. — When Regan Smith passed Tony Stewart on the last lap at Talladega Superspeedway, he was certain he'd just earned his first Sprint Cup Series victory.

When NASCAR ruled the pass illegal, Smith figured he was for sure a career-best second. Still unhappy with his runner-up finish, he went to argue his case in the NASCAR office following Sunday's finish.

So imagine his surprise, while waiting for top NASCAR officials, Smith saw himself dropped to an 18th-place finish.

"I thought I was going to plead my case about if I was first or second," Smith said Thursday. "I was sitting in the (NASCAR) hauler, literally sitting there, and it flashed up on the screen and it went from second down to 18th.

"And I said 'Whoa, whoa, whoa, what just happened there?' I was like 'Man, that's even worse yet."'

And so went the saga of the rookie who appeared to use a gutsy move to beat a two-time series champion in a thrilling Talladega finish. Instead, Smith's pass of Stewart under the yellow out-of-bounds line at the bottom of the track was disqualified and his penalty was being dropped to the tail end of the lead lap.

"If we were to go back two weeks from now, same situation, same circumstances at the end of the race, knowing what I know now, there would have been a big crash at the end of the race because I wouldn't have budged," Smith said. "I would have stuck my nose there and left it there."

"I feel bad for him because it was the race of his life," Stewart said. "I sympathize from his standpoint, and it's frustrating when you know that at the very least you should have finished second,