When the first round ended, Aaron Simpson was in complete control of his UFC on FX 5 matchup with Mike Pierce. He slammed Pierce to the ground, nearly locked in a rear naked choke, and closed out the opening five minutes with some ground and pound. On the scorecards, it was clearly a dominant round for him.

After the one-minute rest period ended, Pierce reversed momentum in an instant.

Pierce caught the charging Simpson with an uppercut just seconds into the round, and finished him with a pair of ground strikes for a stunning second-round TKO.

The finish came at 29 seconds of the round.

The knockout win came as a bit of a shocker, especially given Pierce's propensity to go the distance. He had only two finishes in his previous nine UFC fights.

"It's been a while since I've had a finish and I love knockouts more than anything, so I'm thrilled," he said afterward.

It was his third win in his last four fights overall, as he improved to 15-5.

"It felt great," he said. "He walloped me pretty good in the first but I don't give up easy."

It was the first loss as a welterweight for Simpson, who won in his divisional debut in July. He's now 12-4 overall. It was only the second time in his career he's been finished.