After the 13th stage, the top standings didn't change: Wiggins leads second-place Sky teammate — and fellow Briton — Christopher Froome by 2 minutes, 5 seconds. Nibali is third, 2:23 back, and defending champion Cadel Evans of Australia is 3:19 back in fourth.
Some race watchers say Wiggins should keep on good terms with his own teammate, Froome, who won on an uphill finish in Stage 7, and finished second to Wiggins in a time-trial into Besancon two days later.
"The most important thing for Sky is that those two guys remain friends until the end," said Saxo Bank team manager Bjarne Riis. "But I can't answer whether it will be the case or not."
Said Stefano Zanatta, sports director of Nibali's Liquigas team: "If Wiggins and Froome don't get along well together, we'll try to make the most of it."
Wiggins, too, senses speculation about a possible conflict of interest, even if Froome has publicly expressed support for his Sky leader. Asked whether he considered Froome an opponent, Wiggins replied with a chuckle: "Well, he is a teammate."
Saturday's route was known as a transitional stage because it was mostly flat, and guided riders away from their last big test — the Alps — and toward their next, the Pyrenees.
As the riders neared the coast, the stage's big challenges arrived: A steep if short climb in the port town of Sete, and a windy ride between the Mediterranean and the Bassin de Thau, known for its oyster farms.
Riders swung their bikes left to right as if in slow motion as they hit the Mont Saint-Clair climb in Sete, a mid-grade ascent over 1.6 kilometers — but with an average gradient of 10.2 percent.
That split the pack into several groups with Greipel, Wiggins, Nibali among the first 43 riders to finish. Some sprinters, like Mark Cavendish of Britain and Matt Goss of Australia, were dropped on the Mont Saint-Clair and came across more than 8 1/2 minutes later.
Sunday's 14th stage takes riders along two big climbs in a 191-kilometer trek from Limoux to Foix.
Associated Press writers Greg Keller and Samuel Petrequein in Le Cap d'Agde contributed to this report.
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