Three-time champion Alberto Contador mixed up the Tour de France overall standings with a powerful move on the Col de Manse.
While the same seven contenders topped the standings after the 17th stage Tuesday, Contador moved up a spot to sixth. Thor Hushovd won the stage in a breakaway.
Contador, baring his teeth as his tires sizzled on the rain-slick roads, surged out of the pack on the mid-grade Col de Magne climb, and held on through a treacherous downhill finish in the 101-mile ride from Saint-Paul-Trois-Chateaux to Gap.
"I knew I needed to attack," Contador said. "I couldn't care less if someone kept on my wheel — I knew one of them would fail. I'm so happy. It has been a major gap, much bigger than I expected."
The unexpected surge by the Spaniard shook up the leaderboard at cycling's greatest race, which ends Sunday in Paris after a jaunt Wednesday into Italy, then two days in the Alps, and a time-trial Saturday in Grenoble.
Among the contenders, only Cadel Evans kept up. The Australian actually outpaced Contador by 3 seconds at the end. But Contador, who lost time with crash trouble earlier in the race — trimmed 18 seconds off his deficit to overall race leader Thomas Voeckler of France, cutting it to 3 minutes, 42 seconds.
More importantly, the Spaniard recovered more than a minute on his runner-up at the last two Tours, Andy Schleck, a top climber who almost inexplicably didn't keep up on the relatively easy final ascent.
Schleck conceded he was "disappointed," but that "there are other chances to take back time." His biggest ally — his older brother and Leopard Trek teammate Frank Schleck — said they hadn't foreseen the attack.
"We were a bit surprised that Contador went on the climb," Frank Schleck said. "We know that he is a rider that attacks when he has good legs, but we had anticipated he would wait for the Alps."
Contador's Saxo Bank team could hardly contain its joy.
"He put the hammer down and showed he's still there in the game," manager Bjarne Riis said. "I'm happy for that."
Aside from the aggressive Contador, the other standout was Evans, a two-time runner-up who has so far had a nearly flawless race — and showed he's not giving up to the Spaniard without a fight.
"Today was an opportunity for us to see what could happen," said Jim Ochowicz, manager of Evans' BMC squad. "We assumed that at some point Contador was going to try to take some time back. His move, when he made it, was the perfect opportunity for Cadel to counter."
Voeckler knows Contador is often better than he is in mountain climbs and the time trial — and expects to lose the yellow jersey soon.
"I kept it by a handful of seconds, but that shows that I've hit my ceiling," Voeckler said.
Hushovd, a Garmin-Cervelo rider who wore yellow for six days in the first week and also won Stage 13, led a three-man breakaway — edging Norwegian compatriot, Edvald Boassen Hagen and teammate Ryder Hesjedal of Canada.
Evans finished 4:23 back in 11th place. Voeckler and Frank Schleck crossed 21 seconds later. Andy Schleck was 1:09 slower than the Australian — and 1:06 behind Contador.
Overall, Evans climbed to second, 1:45 behind Voeckler. Frank Schleck, now third, was 1:49 back. Andy Schleck remained fourth, 3:03 back.
Andy Schleck complained on Twitter about a quick succession of drug tests Saturday, including one in a restaurant where he had to carry a urine sample as others were dining.
The International Cycling Union and France's anti-doping agency are doing hundreds of doping checks during the race. UCI officials have been unapologetic about the intensity of its doping controls.
Contador tested positive for clenbuterol at the 2010 Tour, but has denied wrongdoing. He is riding this year because the Court of Arbitration for Sport hasn't ruled on his case yet. He could be stripped of his 2010 title if it rules against him next month.
The three-week race veered into Italy on Wednesday for a 111-mile ride from Gap to the Italian town of Pinerolo.