Four-time champion Primoz Roglic finished fourth on stage 18 but only cut his overall deficit to Enric Mas by 33 seconds, leaving the Spaniard with one hand on the Vuelta a Espana trophy with just three stages remaining.
None of the riders in the general classification top 10 had ever beaten Roglic in a time trial and that remained the case at the end of the day in Jerez de la Frontera.
But Mas produced one of the best TTs of his life to limit the damage going into a blockbuster final weekend on mountainous terrain, where he has shown himself to be the best rider in this race.
This was expected to be the biggest test of this race for the 31-year-old, who grinned as he crossed the line having successfully navigated it – and now has a maiden Grand Tour victory in sight.
Setting off from the bullring in El Puerto de Santa Maria, the riders tackled a flat 32.1km route to Jerez de la Frontera, a course perfectly designed for time-trial specialists and a nightmare for the purer climbers.
The stage was won by two-time European time trial champion Stefan Kung, who was visibly relieved as Roglic – one of the favourites for the day – failed to better his time of 35:22.82, finishing 18 seconds down. It was Kung’s 24th professional victory in a time trial and his second at the Vuelta.
Roglic’s Red Bull-Bora-Hansgrohe teammate, British rider Callum Thornley, was second, three seconds behind – his best-ever result in a WorldTour race and on his debut grand tour – with Joao Almeida of UAE Team Emirates-XRG third, eight seconds off the pace.
While he may not have added to his 15 career Vuelta stage wins Roglic did move up a position in the general classification standings to second, gaining almost a minute on Felix Gall, who slipped to third.
Mas now leads Roglic by 1’37” and Gall by 3’01”, with Richard Carapaz fourth at 5’17”.
Britain’s Oscar Onley produced a strong ride to nearly double his lead over Jakob Omrzel in the best young rider’s classification.
The 23-year-old finished 27 seconds quicker than the young Slovenian having been only 30 seconds ahead of him at the start of the day, with his grasp on fifth place overall also slightly more secure as a result.
The other big success story of the day was Frenchman Clement Berthet, who leapt from ninth to seventh overall, while there was disappointment for Lidl-Trek’s Mattias Skjelmose, normally a strong time-triallist, who slipped to eighth. 2023 champion Sepp Kuss fell out of the top 10.
The race continues on Friday with a 210km mountain stage from Velez-Malaga to a summit finish at Penas Blancas, Estepona.
