Italian Giuseppe Guerini clinched a surprise victory in the 19th stage of the Tour de France.
The T-Mobile rider produced a devastating attack with just over a kilometre remaining and the three alongside him were unable to respond.
Frenchman Sandy Casar finished second in the shortest road stage of the Tour, ahead of Franco Pellizotti of Italy.
Oscar Pereiro came fourth to force his way into the overall top 10, with Lance Armstrong finishing safely in the pack.
The American, heading for his seventh Tour de France victory on Sunday, has a lead of two minutes 46 seconds over Italian Ivan Basso.
He will look to tighten his stranglehold on Saturday in what will be his last ever time trial before his retirement.
"I probably have five more hours in my career as a cyclist. I'm not terribly sad about that," said the 33-year-old.
Guerini's only other stage win came in 1999 at the Alpe d'Huez, when he was famously knocked over by an over-enthusiastic spectator.
There was no such drama for the 35-year-old on Friday.
His attack on a slight incline surprised his three rivals to such an extent that they did not give chase.
It was Frenchman Casar of Francaise des Jeux who had initiated the day's first attack which led to the four riders emerging at the front.
They led by a slim margin for much of the way over the hilly terrain in the Puy-de-Dome and the Loire.
However, the six chasers behind could not combine to close the gap.
Italian Salvatore Commesso launched several bids to attack the front four but was repeatedly caught.
The peloton, including all the main general classification riders, showed little interest in chasing them down, especially with the difficult 55.5km time trial in St Etienne to come on Saturday.
At the front, Pereiro, who won the 16th stage and has been at the front in almost all of the mountain stages, looked favourite but Guerini's attack surprised everyone.
"I knew that Pereiro was thinking more about his overall placing and that Casar and Pellizotti were probably faster than me," said the Italian.
"That's why I attacked so far from the line."
Stage result (Top 10)
1. Giuseppe Guerini (Ita) T-Mobile 3:33:04
2. Sandy Casar (Fra) Francaise des Jeux at 10 seconds
3. Franco Pellizotti (Ita) Liquigas at same time
4. Oscar Pereiro (Spa) Phonak at 12 seconds
5. Salvatore Commesso (Ita) Lampre - Caffita at 2:43
6. Kurt-Asle Arvesen (Nor) Team CSC at 2:48
7. Nicolas Portal (Fra) AG2R at same time
8. Bert Grabsch (Ger) Phonak at same time
9. Sylvain Chavanel (Fra) Cofidis at same time
10. Pieter Weening (Ned) Rabobank at 3:50
Overall standings (Top 10)
1. Lance Armstrong (USA) Discovery Channel at 81:22:19
2. Ivan Basso (Ita) Team CSC at 2:46
3. Mickael Rasmussen (Den) Rabobank at 3:46
4. Jan Ullrich (Ger) T-Mobile at 5:58
5. Francisco Mancebo (Spa) Illes Balears at 7:08
6. Levi Leipheimer (USA) Gerolsteiner at 8:12
7. Cadel Evans (Aus) Davitamon-Lotto at 9:49
8. Alexandre Vinokourov (Kaz) T-Mobile at 10:11
9. Floyd Landis (USA) Phonak at 10:42
10. Oscar Pereiro (Spa) Phonak at 12:39