The planned 199-kilometre mountains stage had been expected to be a key day in the general classification battle, but it was cut to just 74.6km following heavy rainfall.

Riders completed the neutralised section of the originally planned start in Borgofranco d'Ivrea, before travelling to Le Châble in Switzerland at the bottom of the Croix de Coeur for the beginning of the revised route.

The final part of the stage featuring a sharp climb up to Crans-Montana in Switzerland was unchanged.

Organisers said the application of the extreme weather protocol met "the athletes' demands".

Association of Professional Cyclists President Adam Hansen said more than 90 per cent of riders on the Giro had voted in favour of invoking the protocol, and insisted "the weather conditions experienced during this year's Giro have been among the most intense".

Overall leader Geraint Thomas of Britain said it was "the best decision" and a "decent compromise", as reported by Eurosport.

When the stage belatedly got underway, there was no change at the top as Thomas preserved a two-second lead for the Ineos Grenadiers over Team Jumbo-Visma's Primož Roglič from Slovenia.

The Ineos Grenadiers controlled the pace of the general classification group up the final climb, and there was little in the way of attacks from Jumbo-Visma.

Thomas suggested Roglič is happy to bide his time with a further eight stages to come up to the finale in Rome on May 28.

"The way it went at the end made it quite hard to attack," he said.

"But Primož is probably happy to leave me in the Maglia Rosa [pink jersey] for a few more days.

"I expect something more from him next week."

Portuguese leading young rider João Almeida of UAE Team Emirates remains third overall at 22 seconds off the pace.

All three riders finished the stage in 2 hours 17min 56sec.

Team DSM's Andreas Leknessund of Norway lost a further seven seconds on Thomas and is now 42 seconds adrift in fourth overall.

Much of the drama unfolded at the front of the race, where six-time Grand Tour stage winner Pinot in Groupama-FDJ colours wanted a first Giro victory since 2017 on what could be his final appearance, with the 32-year-old announcing in January he would retire at the end of the 2023 season.

Pinot, Cepeda of EF Education-EasyPost and Movistar Team's Rubio emerged strongest from an initial group of seven.

It was Pinot seeking to make inroads up the Crans-Montana with several attacks to which Cepeda responded.

Tensions flared on the final climb, with Pinot and Cepeda involved in a heated argument up the final climb.

With the focus on the Frenchman and the Ecuadorian, Rubio remained in contention and caught his two rivals with a late surge for the finish line which produced a maiden Grand Tour win and Movistar's first on the Giro for four years.

He triumphed in 2:16:21, ultimately beating Pinot by six seconds and Cepeda by 12.

"A big day that I was looking for by working very hard," Rubio said.

"It’s been difficult with the bad weather.

"But I had to keep going.

"I knew that Pinot was very strong.

"I had to finish with him and play it well tactically.

"It will take time for me to realise that I won a stage of the Giro d’Italia.

"I didn’t believe I’d do it."

Pinot climbed into the top 10 of the general classification, but cut an emotional figure having been denied the stage win and remains 3min 13sec adrift of Thomas.

He reclaimed the blue jersey after returning to the top of the mountains classification on 114 points as a consolation, giving him a 10-point advantage over Eolo-Kometa's Davide Bais competing on his home Grand Tour.

Another Italian in Jonathan Milan of Team Bahrain Victorious now holds a significant lead of 76 in the points classification, after Trek-Segafredo rider Mads Pedersen of Denmark became the latest high-profile athlete to drop out of the race because of a sore throat and tracheitis.

Tomorrow's 193-kilometre stage is set to begin in Sierre in Switzerland and features a top-category climb up the Simplon Pass near the start, but afterwards is a mostly flat ride to Cassano Magnago in Italy.