Wiggins slid off on a right-hand bend in slippery conditions and although he got back on his bike he lost valuable time and has slipped from sixth to 23rd place in the overall standings.
Australian Adam Hansen won the stage after a fine solo effort that saw him cross the finish line more than a minute ahead of Enrico Bataglin and Danilo Di Luca.
Movistar rider Benat Intxausti assumed the overall leader's pink jersey from Luca Paolini, who slumped to 15th place. Intxausti holds a five-second advantage over Vincenzo Nibali in second, with Ryder Hesjedal a further three seconds back.
Wiggins' misfortune has left him one minute and 32 seconds adrift of the new leader and means he will head into Saturday's stage eight time trial looking to haul himself back in contention.
Hansen was one of a group of six riders who sprang clear midway through the stage but the breakaway soon collapsed to just the Australian and Emanuele Sella, who himself crashed and was swallowed up by the chasing group.
Hansen, riding for the Lotto Belisol team, was left to cruise home alone one minute and seven seconds ahead of his nearest rival Bataglin.