Frascati - Movistar's Giro d'Italia contender Richard Carapaz won stage four on Tuesday as a mass fall in the peloton seven kilometres from the finishing post cost 2017 champion Tom Dumoulin a devastating four minutes in the overall standings.
Dumoulin came second at both the Giro d'Italia and the Tour de France in 2018, as well as winning the 2017 Giro and the 2017 world championships time-trial, making him a chief contender in all major tours and races.
The fall saw a small group of eleven riders get away from the peloton, including overall leader Primoz Roglic and two of his chief contenders to win the Giro, Britain's Simon Yates and Astana's Miguel Angel Lopez.
Ecuador's Carapaz made a long-range sprint for the line from more than 400 metres out with only Australia's Caleb Ewan and UAE's Diego Ulissi capable of challenging and ending second and third respectively.
Roglic, a former ski jumper, finished two seconds behind this trio, gaining 16 seconds on all his chief rivals for the 2019 title.
Dutchman Dumoulin freewheeled most of the way to the finishing post after his fall with blood streaming from a knee, with his chances of winning the title in tatters.
He was then whisked away to hospital for x-rays as he said he was unable to bend his knee.
Sunweb sports director Michiel Elijzen admitted Dumoulin's chances had been massively compromised.
"It looks like its over for the GC," he said referring to the overall standings.
"It's hard. We came here to win the Giro," he said.
"But after four stages if you are four minutes off the leader..."
"We just have to wait and see if he can continue in the Giro," he said.
Wednesday's fifth stage is a short 140km run from Frascati, just south of Rome, to Terracina where a 1.5km home straight should provide a perfect platform for a spectacular sprint finish. `
Results and standings after Tuesday's fourth stage of the Giro d'Italia, a 223km run from Orbotello to Frascati:
1. Richard Carapaz (ECU/Movistar) 5hrs 58min 17sec, 2. Caleb Ewan (AUS/LOT) s.t., 3. Diego Ulissi (ITA/UAE) s.t., 4. Pascal Ackermann (GER/BOR) at 02sec., 5. Florian Senechal (FRA/DEC) 02., 6. Primoz Roglic (SLO/JUM) 02., 7. Valerio Conti (ITA/UAE) 14., 8. Miguel Angel Lopez (COL/AST) 18., 9. Arnaud Demare (FRA/FDJ) 18., 10. Simon Yates (GBR/MIT) 18., 11. Rafal Majka (POL/BOR) 18., 12. Bauke Mollema (NED/TRE) 18., 13. Davide Formolo (ITA/BOR) 18., 14. Tony Gallopin (FRA/ALM) 18., 15. Vincenzo Nibali (ITA/BAH) 18, 16. Bob Jungels (LUX/DEC) 18.
1. Primoz Roglic (SLO/Jumbo) 16hr 19min 20sec, 2. Simon Yates (GBR/MIT) at 35sec, 3. Vincenzo Nibali (ITA/BAH) 39, 4. Miguel Angel Lopez (COL/AST) 44, 5. Diego Ulissi (ITA/UAE) 44, 6. Rafal Majka (POL/BOR) 49, 7. Bauke Mollema (NED/TRE) 55, 8. Damiano Caruso (ITA/BAH) 56, 9. Bob Jungels (LUX/DEC) 1:02, 10. Davide Formolo (ITA/BOR) 1:06.