Primoz Roglic placed himself in pole position to retain his Vuelta a Espana title with a sensational time trial display as Briton Hugh Carthy impressed to stay in contention.
Jumbo-Visma's Roglic took stage 13 and now holds a 39-second advantage over Ineos Grenadiers' Richard Carapaz, having overturned his 10-second lead.
Carthy ate away at the 32-second gap to Carapaz during the 33.7km stage.
He stays third overall but is now only eight seconds behind the Ecuadorian.
Five stages remain, with the riders now set for a hilly stage 14 covering 204.7km between the Galician city of Lugo and Ourense, which the Vuelta last visited in 1960.
Slovenian Roglic will be a strong favourite for the title although he was philosophical about his chances.
The 31-year-old said: "I felt strong - surprising. I thought I'd suffer a lot more.
"Today went quite fine. We know it's not a fun thing to do the time trial, but I had the legs. I'd rather be 39 seconds ahead than behind, but we need to keep our focus."
Roglic was fancied to do well in Tuesday's time trial and slowly began chipping away at Carapaz's advantage after he set off from Muros.
It was a smooth change from his time trial bike to a more traditional road bike before the final ascent up Mirador de Ezaro, which he coped with better than Carapaz.
The Slovenian clinched the stage from American Will Barta of the CCC team.
Carthy, who won stage 12, had cut the deficit to the leading pair during the first half of the race, but could not match Roglic in the closing kilometres.
Stage 13 result
1. Primoz Roglic (Slo/Jumbo-Visma) 46mins 39secs
2. Will Barta (US/CCC Team) +1sec
3. Nelson Oliveira (Por/Movistar) +10secs
4. Hugh Carthy (GB/EF Pro Cycling) +25secs
5. Bruno Armirail (FRA/Groupama-FDJ) +41secs
6. Mattia Cattaneo (Ita/Deceuninck-Quick-Step) +46secs
7 Richard Carapaz (Ecu/Ineos Grenadiers) +49secs
8. Remi Cavagna (Fra/Deceuninck-Quick-Step +58secs
9. David De La Cruz (Spa/UAE) +59secs
10. Jasha Sutterlin (Ger/Team Sunweb) +1min 7secs
General classification after stage 13
1. Primoz Roglic (Slo/Jumbo-Visma) 49hrs 16mins 16secs
2. Richard Carapaz (Ecu/Ineos Grenadiers) +38secs
3. Hugh Carthy (GB/EF Pro Cycling) +47secs
4. Dan Martin (Ire/Israel Start-Up Nation) +1min 42secs
5. Enric Mas (Spa/Movistar) +3mins 23secs
6. Wout Poels (Ned/Bahrain-McLaren) +6mins 15secs
7. Felix Grossschartner (Aut/Bora-Hansgrohe) +7mins 14secs
8. Alejandro Valverde (Spa/Movistar) +8mins 39secs
9. Aleksandr Vlasov (Rus/Astana) +8mins 48secs
10. David de la Cruz (Spa/UAE) +9mins 23secs