Chaves takes mountain win, Martin builds Swiss lead
Esteban Chaves of Columbia celebrates on May 16, 2014 in Wrightwood, California - by Ezra Shaw
Orica-GreenEdge rider Chaves finished three seconds ahead of Czech Roman Kreuziger and Dutchman Bauke Mollema in the Valais ski resort, with the chasing group that included Martin crossing 17 seconds behind.
It was a second win this season for Chaves, 24, who also won a stage at last month's Tour of California.
Meanwhile, triple world time-trial champion Martin, who has worn the leader's yellow jersey since winning last Saturday's opening time-trial, extended his lead over Dutchman Tom Dumoulin to 51sec.
Two-time defending champion Rui Costa of Portugal is lurking, 1min 05sec adrift in third.
A group of six riders broke free of the pack early into the 219km ride from Delemont and the escapees would open up a lead of over six minutes before the peloton made a concerted effort to gradually reel them in.
Several teams jostled for position at the head of the pack while Omega Pharma-Quick Step did their best to keep Martin as fresh as possible for the back-to-back climbs at the finish.
Movistar's Jose Joaquin Rojas was the first of the escapees to reach the top of the initial category three climb, and it was then the turn of Team Sky rider Christian Knees to try his luck on the final ascent.
BMC's Danilo Wyss subsequently decided to make his move but the peloton was too strong and IAM Cycling set up home favourite Mathias Frank for a strong finish while Martin continued to battle to keep up with the pacesetters.
Kreuziger matched Frank all the way as the Swiss rider tried to launch an attack before the pack swallowed them up, leaving it to Chaves to jump clear of the field inside the final two kilometres and secure an impressive win in Verbier.
Sunday's final stage is a gruelling 157km ride from Martigny to Saas-Fee that finishes with a beyond category climb.