Kazakh Alexey Lutsenko led Spaniard Ion Izagirre in an Astana 1-2 in Wednesday's fourth stage of the Criterium du Dauphine, a 16.4km time-trial between Firmigny and Roche-la-Moliere.
Bora-Hansgrohe's Austrian Lukas Postlberger kept hold of the race leader's yellow and blue jersey, but Lutsenko cut his lead to just one second.
"I rode to my maximum, even if it looks a bit surprising," said the 28-year-old, who places himself as a contender with this result.
Ineos Grenadiers' 2018 Tour de France winner Geraint Thomas was leading halfway through the course, but slowed down in the second, more demanding half.
The Welshman eventually finished, like Postlberger, 23sec off Lutsenko's winning time.
Thomas' teammate Richie Porte is now Ineos' top ranked rider at just 15sec, while the 2020 Giro d'Italia winner Tao Geoghegan Hart is at 1min 03sec.
"The pacing was a bit too aggresive for what I had today. I just felt like I was legless," Thomas said in a video posted by Ineos on Twitter.
"Richie's still up there and I'm there or there abouts so still all to play for."
Former Ineos rider and four-time Tour de France champion Chris Froome had another difficult day in the saddle, finishing 93rd at 2min 12sec.
Froome is on an epic bid to regain full fitness after suffering dreadful injuries on this race in 2019, a bid which appears stuck in a low gear for now.
In his prime Froome might have expected to win this kind of stage.
Thursday's fifth stage is a 175.4km ride from Saint-Chamond to Saint-Vallier, featuring a steep climb 12km from the finish that will complicate affairs for the sprinters.