(CNN) Defending champion Geraint Thomas made up nearly half a minute on leader Julian Alaphilippe in a gripping 15th stage of the Tour de France in the Pyrenees on Sunday.

A former winner of the event said the day could be significant in deciding the race's outcome.

Thomas shaved off 27 seconds, pulling away from the less experienced Alaphilippe with around 1.5 kilometers (0.93 miles) remaining in the 185-kilometer (115-mile) section between Limoux to Foix Prat d'Albis. He now trails Alaphilippe by one minute, 35 seconds.

"Geraint will now start to think he can win this race again," said 2012 champion Bradley Wiggins, analyzing the race for British Eurosport.

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Wiggins said Alaphilippe's failure to pace himself cost him in the stage and could hurt his overall chances as he bids to become the first Frenchman to win cycling's most famous race since Bernard Hinault in 1985.

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