Simon Yates (Mitchelton-Scott) "got carried away" attacking on the finishing climb of Vuelta a España stage four near Granada, but doing so took precious time on his overall rivals early into the three-week race.
The Brit gained 27 seconds on race leader, Sky's Michal Kwiatkowski (Sky). He moved from ninth to third overall at 10 seconds from Kwiatkowski. Emanuel Buchmann (Bora-Hansgrohe) is second overall at seven seconds.
"It wasn't the plan, I got carried away but I felt good and I saw an opportunity there," Yates said.
"Lotto-Jumbo were running a good tempo through the town but seemed to fall apart or slow down a bit and I thought I would keep going and that was it really."
Benjamin King (Dimension Data) won from an escape. Behind, the overall favourites marked each other, including Kwiatkowski, Alejandro Valverde (Movistar) and Fabio Aru (UAE Team Emirates).
Yates attacked with around three kilometres left in the 12.4-kilometre climb to Alfacar, north of Granada. Valverde tried to follow, but the 26-year-old was free.
Yates closed at 2-48 minutes from the winner and Kwiatkowski 3-15. Others including Richie Porte and Vincenzo Nibali, both suffering, lost time.
"I don't really know what I was doing. Maybe I was testing the guys and was thinking someone would come with me straight away but that was that," Yates said.
"I didn't mean to. I'm not trying to be cocky or anything, it was just one of those things and when I tried once, I got away.
"It looks like I have gained the time I lost in the other part of the race, in the prologue and the other day with the little kicker, so yeah, it was a good day."
It was a good move for Yates who led the Giro d'Italia for 13 days and won three mountain stages along they way in the pink jersey. He crumbled near the end of the race, stage 19, seeing Chris Froome (Sky) go on to win the race overall two days later.
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