Sir Bradley Wiggins lost 17 seconds and fell to sixth overall at the Giro d'Italia after being caught behind a late crash on a wet and treacherous fourth stage.
The Team Sky leader had dropped back from the head of the race going into the day's finale in Serra San Bruno and was then held up when three riders fell ahead of him in heavy rain.
He eventually finished 48th, well adrift of a front bunch including his two main rivals for overall victory, Vincenzo Nibali and Ryder Hesjedal.
It means that the slender advantage Wiggins had built up in Team Sky's team time trial victory on stage two has now been eroded. Nibali (Astana) has overturned a 14-second deficit and leads Wiggins by three seconds, while Hesjedal (Garmin-Sharp) has drawn level with the Briton on the same time.
Although the crash happened inside the final 3km, the race jury awarded only the three riders who fell the same time as the stage winner, Italy's Enrico Battaglin.
The Bardiani Valvole - CSF Inox rider prevailed from a reduced-bunch sprint ahead of Fabio Felline (Androni Giocattoli) in second and Giovanni Visconti (Movistar) in third, while overnight leader Luca Paolini (Katusha) finished tenth to retain the pink jersey.
'One of those races'
Team Sky sports director Marcus Ljungqvist told teamsky.com after the stage: "Brad was caught behind a crash. It is one of those things that happens in bike racing. It is certainly not the end of the world."
Team Sky principal Sir Dave Brailsford added on Sky Sports News: "It is one of those races where you just have to pay attention all the time. You can gain hard-earned seconds here and there and then you can lose time very quickly. Ultimately, this first week is all about staying in contention and then this race will be won and lost in the time trials and the high mountains."
The day was the second longest of the Giro at 246km and while the first 190km were largely dry and flat, the last 56km took place over two categorised climbs and in wet and cloudy conditions.
Seven riders headed up the road early on and although they built up an advantage of almost eight minutes, three men later fell off the pace and then the remaining four riders' advantage began to plummet on the first climb of the day.
The last escapee was caught close to the summit of the category-three ascent to Vibo Valentina, 42km from home, prompting a series of attacks from out of the peloton on the descent and subsequent last climb of the day, the category-two Croce Ferrata.
Patrick Gretsch (Argos-Shimano), Stefano Pirazzi (Bardiani Valvole - CSF Inox), Frederik Willems (Lotto-Belisol), Marco Marcato (Vacansoleil-DCM) and Sylvain Georges (Ag2r-La Mondiale) all tried and failed to go clear, before Danilo Di Luca (Vini Fantini) and Robinson Chalapud (Colombia) finally made an escape stick 10km out, just below the Croce Ferrata summit.
The duo maintained their gap on the downhill to the finish line, but were caught inside the final kilometre, paving the way for Battaglin to win the bunch sprint.
Watch highlights of the stage on Sky Sports 4 from 7pm
Stage four result
1 Enrico Battaglin (Ita) Bardiani Valvole - CSF Inox, 6:14:19
2 Fabio Felline (Ita) Androni Giocattoli, st
3 Giovanni Visconti (Ita) Movistar, st
4 Rigoberto Uran (Col) Team Sky, st
5 Arnold Jeannesson (Fra) FDJ, st
6 Cadel Evans (Aus) BMC, st
7 Benat Inxausti (Spa) Movistar, st
8 Ryder Hesjedal (Can) Garmin-Sharp, st
9 Robert Kiserlovski (Cro) RadioShack-Leopard, st
10 Luca Paolini (Ita) Katusha
13 Vincenzo Nibali (Ita) Astana, st
48 Bradley Wiggins (GB) team Sky, +17secs
1 Luca Paolini (Ita) Katusha, 15:18:51
2 Rigoberto Uran (Col) Team Sky, +17secs
3 Benat Intxausti (Spa) Movistar, +26
4 Vincenzo Nibali (Ita) Astana, +31
5 Ryder Hesjedal (Can) Garmin-Sharp, +34
6 Sir Bradley Wiggins (GB) Team Sky, same time
7 Giampaolo Caruso (Ita) Katusha, +36
8 Sergio Henao (Col) Team Sky, +37
9 Mauro Santambrogio (Ita) Vini-Fantini, +39
10 Cadel Evans (Aus) BMC, +42
Red (points classification) - Cadel Evans (BMC)
Blue (mountains classification) - Giovanni Visconti (Movistar)
White (best young rider) - Fabio Aru (Astana)