Australian Rohan Dennis snatched the race leader's yellow jersey of the Criterium du Dauphine after Wednesday's fourth stage, which was won by Germany's Tony Martin.
Garmin rider Dennis, a silver medallist in the team pursuit at the London Olympics, was second in the 32.5km time-trial, 47sec behind Omega-Pharma's Martin, the reigning world champion in the discipline.
But there was woe for Spaniard Alberto Contador, who could only finish 61st, and who now sits 2min 45sec behind Sky's British rider Chris Froome.
Spain's Joaquim Rodriguez, another favourite for a podium spot in the Tour de France's warm-up race, is 2min 56sec off Froome.
In the overall standings, Dennis stands 5sec ahead of Froome.
"I knew my form was good," said Dennis. "It can always be a bit of a gamble against guys like Froome and Contador.
"I'm surprised to be so close to Martin. This is the best time-trial I've done to date.
"I just tried to hold the power...and instead of dropping towards the end, I realised I had a bit more to give."
Froome was left satisfied with his performance but mystified by Contador's tactics.
"Of course, it's a good result for me", Froome said. "Today it was a good exercise and a good test for the form.
"I had good legs. I don't know what Alberto's strategy is. Maybe he's keeping some energy for the mountains."
Contador admitted that "it was not a good day for me".
"I didn't have much energy in the legs, but there is still time before my form reaches the top," he told French television.
"I hope to be better and better each stage. For the Tour de France, there's still time. I knew that Chris Froome was superior in time trialling."
Thursday's fifth stage is a tough 139km ride from Gresy-sur-Aix to the ski resort of Valmorel.