The Colombian slid down the general classification after falling behind on the first climb of Stage 10 last Tuesday.
He had earlier won the Mount Etna stage (Stage 6) and was sitting pretty in second place overall behind Mitchelton-Scott teammate Simon Yates – the current race leader.
The 25-minute loss, however, put him down in 39th. The next day he lost another five minutes as his hopes of victory were ended.
The disastrous 10th stage followed the first full rest day and may have been part of the problem. Some riders do not perform well after a rest day.
A week has passed but Chaves is still not sure of the reason behind his woes, and he has yet to undergo deep medical checks to try to find out what happened.
“That will take time for sure,” he told VeloNews. “There is no one-word answer from one day to the other or one night, now we just need to fight for the pink and this is it.”
But Tour de France champion Chris Froome, who won on Saturday’s Monte Zoncolan summit finish, lost more time on the 176km Dolomites stage from Tolmezzo to Sappada, slipping to seventh overall and nearly five minutes behind his countryman.
Mitchelton-Scott’s Yates launched his attack 17km from the finish line on the penultimate climb and held on to add to his previous victories on the ninth stage at Gran Sasso and 11th at Osimo.
He crossed the line 41 seconds ahead of a group led by Colombian Miguel Angel Lopez of the Astana Pro Team, with Team Sunweb’s Tom Dumoulin of the Netherlands in third.
“My attack was a little bit on instinct,” explained Yates. “I saw a little gap. I gave everything the second time to get away. It’s fantastic.”
Defending champion Dumoulin is second overall but drops to 2min 11sec behind Yates going into the final week with the race finishing in Rome next Sunday.
📸 Best pics from Stage 15, Tolmezzo - Sappada. Which one do you like the most? | 📸 Le migliori immagini della Tappa 15, Tolmezzo - Sappada. Qual è la tua preferita? | 📸 Las mejores imágenes de la Etapa 15, Tolmezzo - Sappada. ¿Cual prefieres? https://t.co/haOAnSRKxj#Giro101 pic.twitter.com/p0rJUQGEzU— Giro d'Italia (@giroditalia) 20 May 2018
Monday’s final rest day will be followed by a time-trial at Rovereto on Tuesday where Dutchman Dumoulin is expected to gain time.
“I feel emotional after today. I’ve been fighting since Israel to build a good lead,” said Yates.
“I’m happy with the gap I have now but it’s far from over. It could vanish in 35 kilometres.”
Italy’s Domenico Pozzovivo finished fourth and is third overall, 2min 28sec behind Yates, with France’s Thibaut Pinot of Groupama fourth overall at 2min 37sec.
Four-time Tour de France winner Froome struggled on the fourth and final climb in the Dolomites losing a minute and a half to spoil his 33rd birthday celebrations.
Froome, helped by teammate Wout Poels who had already proved so valuable on Monte Zoncolan, tried to claw back time on the overall leaders but was unable to match the change of the pace on the ascent to Costalissoio.
The reigning Vuelta a Espana champion dropped from fifth to seventh overall and is now 4min 52sec behind 25-year-old ‘King of the Mountains’ Yates.
But will Yates’ advantage be enough in Tuesday’s time trial? “I really don’t know,” he said.
France’s Pinot believes the Englishman has done the essential though.
“Yates is untouchable unless he has a major failure,” said Pinot.
“It was better than yesterday at the Zoncolan,” he added. “There are days like this … Today, the slopes corresponded more to me.”
But Pinot lamented a damaging battle between Lopez and Ecuadorian Richard Carapaz for the best young rider’s white jersey.
“There was the squabble between Carapaz and Lopez for the white jersey, they were eye-balling each other, they condemned our little group a little,” said Pinot, who is fourth overall just behind Pozzovivo.
“Maybe we could have caught up with Yates and especially taken time on the others,” added the Frenchman.
Britain’s Chris Froome won the 14th stage of the Giro d’Italia on Monte Zoncolan as compatriot Simon Yates extended his overall lead in the Alps.
With the peloton swiftly breaking up as riders tackled the grueling final climb on the 186km stage from Sanvito Al Tagliamento, Team Sky’s Froome surged clear to win by six seconds.
Mitchelton-Scott ‘s Yates was second – 31 seconds ahead of defending champion and nearest challenger Tom Dumoulin in the battle for the maglia rosa.
With six bonus seconds for finishing second, Yates extended his overall advantage to 1:24.