Valais: Chris Froome took a big step towards winning a third Tour de France as Nairo Quintana`s challenge wilted on Wednesday`s first Alpine stage.
Russia`s Ilnur Zakarin won the 184.5km 17th stage from Bern to Finhaut-Emosson in Switzerland ahead of Sunday`s stage 15 winner Jarlinson Pantano of Colombia.
Froome put in a burst inside the final 2km to chase after former Sky team-mate Richie Porte of Australia and put time into all his other rivals.
Quintana, who was the first to respond to Porte`s attack and then Froome`s counter, cracked badly and lost 28sec to the race leader.
The 26-year-old Colombian -- second overall to Froome in 2013 and 2015 -- remains fourth but is drifting away from even a podium finish, now 3min 27sec behind Froome.
"He (Quintana) tried one time (to attack) but maybe he didn`t have the legs like last year," said Froome.
"It was tough but I`m happy to follow the best -- Richie Porte today was very strong on the final climb.
"It`s never easy but maybe I feel better in the third week than last year, for sure."
A young star was born as Adam Yates resisted the best of the rest and lost only 8sec to Froome.
He stays third, but at 2:53 he is now only 26sec behind second-placed Bauke Mollema of the Netherlands, who gave up 40sec to the race leader.
Tasmanian Porte, 31, who has been the only rider to remain alongside Froome in all three uphill finishes at this Tour, looks a strong bet for a top-three finish, now moving up to sixth overall at 4:27.
He lost 1:45 due to a late puncture on the second stage and but for that would be second overall.Zakarin was part of an 11-man breakaway that finally got away after 75km of break-neck racing to start the day.
A second pack of eight formed a chase group before three of those bridged over to the leaders to make a 14-strong breakaway.
Once they got clear, the peloton, which had been riding at 52km/h, slowed up considerably and the leaders managed to stretch out their lead to a maximum of just over 13 minutes by the time the final two climbs began.
That was where the stage was sure to be won or lost with a 13km first category climb preceding a 10km hors category one, and only 7km of downhill between the two to gain some respite.
As the peloton hit the foot of the Col de Forclaz, the penultimate climb, Quintana`s Movistar set the pace.
By the top it was the Astana team of Italian Fabio Aru pushing the tempo.
But when the race got to the business end, there was the familiar sight of a posse of Froome`s black-shirted Sky team-mates taking control.
In the breakaway, Pantano and Poland`s Rafal Majka, who would finish third, escaped on the 7km descent before Zakarin joined them once the final climb began.
Zakarin was restless and attacked almost immediately after catching the front two.
Pantano went with him, but when the Russian accelerated again, the Colombian couldn`t follow and eventually finished 55sec back.
"I did my best today. I`m really happy now," said Zakarin. "This result is not a surprise for me."
Ireland`s Dan Martin attacked from the peloton but Sky pair Mikel Nieve and Wouter Poels kept the tempo going and reeled him in.
Porte then launched his attack with Quintana trying to follow.
Froome went after the pair and soon enough dropped Quintana and bridged to his former team-mate.
Quintana was going backwards and was passed by Yates, Frenchman Romain Bardet, Aru and Louis Meintjes of South Africa by the finish.