Ben O'Connor has retained the leader's red, and Kaden Groves the green of the best sprinter, but Australia's hold on the three jerseys of the Vuelta a España is over after one day with Jay Vine dethroned as King of the Mountains.

Vine has been overtaken by his UAE Team Emirates teammate Marc Soler, who now leads by a point in the race for the polka dot jersey after he got into the main breakaway in the 18th stage, but Vine did not.

The combative Spaniard took full advantage, claiming all 15 points on offer in a 179.5km mid-mountain stage through Basque Country roads won by local rider Urko Berrade with a late solo break.

O'Connor (Decathlon AG2R La Mondiale) maintained his five-second lead in the overall standings over Slovenian three-time champion Primoz Roglič (Red Bull-Bora-Hansgrohe) as the pair once again crossed the line together among a large group.

He briefly lost touch with the other general classification rivals with 134km gone when Richard Carapaz (EF Education-Easypost) launched an attack but quickly recovered.

"It wasn't an easy day, much harder than I thought," said the West Australian. "I didn't expect so much to happen on the climb. Complicated day.

"Tomorrow should be easier (tactically), just the final climb to deal with. Today we had to be on the ball the whole time, trying to make sure the right break goes. Tomorrow, 25-minute climb, see where you end up, so much more simple than today.

"We'll see what tomorrow brings, but I still have (the red jersey) tonight."

Stage 19 is a 173.5km route from Logrono to Alto de Moncalvillo that includes that challenging final climb of nearly 10km.

Berrade was greeted emotionally at the finish line by his family and celebrated with his Kern Pharma teammates after the wildcard team's third stage win in their home grand tour.

For the Basque, who was born in the city of Pamplona not far from the route, the win felt especially sweet.

"It's a dream. The stage closer to home, with all my family watching me, friends, in the last stages of La Vuelta," Berrade said.

The northern Spanish terrain proved challenging, with a leading group of 13 riders still together up the final serious ascent before the last 40km to the finish line just outside the village of Maeztu.

Most of the leading group stuck together as they waited for an opportunity to make a late breakaway and Berrade seized his chance on the last climb with less than five km to go.

Switzerland's Mauro Schmid (Jayco AlUla) was second and Spaniard Pau Miquel Delgado (Kern Pharma) third.

Earlier on Thursday it was announced that Wout van Aert (Visma Lease a Bike) will not race again this season.

The Belgian, whose crash on Tuesday propelled Vine and Groves into their jerseys as he had led both categories, suffered a serious knee injury and remains in hospital receiving "intravenous antibiotics to minimise the risk of infection," a statement from Visma said.

Van Aert would have been a strong contender in the road race and individual time trial at the UCI Road World Championships in Zurich later this month.

AAP