Pieter Weening took stage eight of the Tour de France from Andreas Kloden.
The key moment came on the race's first major climb - the second category Col de la Schlucht - at the end of the day.
Race leader Lance Armstrong was left isolated by his team, faced numerous attacks from rivals T-Mobile and had no option but to let Kloden jump clear.
The German caught lone escapee Weening on the summit but was beaten on the finishing line before Armstrong and the big names came in 27 seconds back.
Rabobank enjoyed a good day in the saddle on the race's second-longest stage, a 231.5km route from Pforzheim in Germany across the Rhine and back into France.
As well as celebrating the stage victory through their 24-year-old Tour debutant they saw Mickael Rasmussen assume the polka dot jersey for the best climber.
The Dane took maximum points available on the first three category three climbs of the day.
On the subsequent long, flat middle section two separate groups led the race, the first made up of four riders before seven worked well together before reaching the Col de la Schlucht.
Dane Nicki Sorensen was involved in both breaks and as he and his six co-escapees, among them Weening, bore down on the second category climb they held a lead of more than six minutes.
But Liquigas-Bianchi and Illes Balears drove the peloton and slowly ate into that advantage before the drama of the race's first big climb.
Weening went for broke on the lower slopes and splintered the lead group of seven.
Further down the road the peloton also splintered early before the real excitment started with an attack from T-Mobile's Alexandre Vinokourov, third overall.
Armstrong was left marking every attack with no help from any team-mates who all found the pace too hot and had to shadow a second break from the Kazakhstan rider.
The American eventually opted to stay on Jan Ullrich's wheel, letting Kloden - the third of the T-Mobile trio - race clear to catch Weening.
Last year's second-placed rider achieved that target on the summit but was unable to shake off the Dutchman on the 15km descent and was pipped in a sprint for the line.
Alejandro Valverde won the race for third, leading home a group that included Armstrong who admitted it had been a "tough day" for his team.
"The Tour started today. I was fine but the team did not follow," he said.
"There was really nothing we could do about that, sometimes we have a bad day.
"I think that maybe the team has been working more than we need to this week.
"But I know those guys, they're going to be just as disappointed if not more disappointed than I am, so I'll think they'll get better."
Stage result (Top 10)
1. Pieter Weening (Ned) Rabobank at 5:03:54
2. Andreas Kloden (Ger) T-Mobile at same time
3. Alejandro Valverde (Spa) Illes Balears at 27 seconds
4. Kim Kirchen (Lux) Fassa Bortolo at same time
5. Jens Voigt (Ger) Team CSC
6. Jan Ullrich (Ger) T-Mobile
7. Cadel Evans (Aus) Davitamon-Lotto)
8. Christophe Moreau (Fra) Credit Agricole
9. Chris Horner (USA) Saunier Duval)
10. Alexandre Vinokourov (Kaz) T-Mobile
Overall standings (Top 10)
1. Lance Armstrong (USA) Discovery Channel at 28:06:17
2. Jens Voigt (Ger) Team CSC at 1:00
3. Alexandre Vinokourov (Kaz) T-Mobile at 1:02
4. Bobby Julich (USA) Team CSC at 1:07
5. Ivan Basso (Ita) Team CSC at 1:26
6. Jan Ullrich (Ger) T-Mobile at 1:36
7. Carlos Sastre (Spa) Team CSC at same time
8. George Hincapie (USA) Discovery Channel at 1:47
9. Andreas Kloeden (Ger) T-Mobile at 1:50
10. Floyd Landis (USA) Phonak at same time