Porte (Sky) still began Sunday's mountainous 165km 15th stage from Marostica to the summit finish Madonna di Campiglio.

But to understand how his mind and those of his teammates were, turn the clock back to Saturday …

Porte is seated behind his teammates and staff, and watching on television the very last riders in the 59.4km stage-14 time trial from Treviso to Valdobbiadene finish one by one.

For some time, Porte's teammate Vasil Kiryienka of Belarus has held the fastest time of 1hour 17 minutes 52 seconds, and under rain it is still best as Spaniard Alberto Contador (Tinkoff-Saxo), the second-last starter, charges towards the finish line.

For Porte, the 17th-last starter, there is little to cheer about, even though Kiryienka looks set to win the stage.

Contador is still down on his time, although destined to take back the race lead from Italian Fabio Aru (Astana), the last starter who is struggling on a challenging circuit of which the second half is hilly.

Porte, showered and drinking a smoothie, is crestfallen after his latest set-back – a performance well below par on a stage where he would normally have shone, and ever since the Giro route was announced last year had planned for it to be the stage he might use to achieve what Contador was about to.

With his time of 1h 22m 12s after suffering from injuries to his left hip and knee from a crash the day before, Porte is wrestling with the reality that his already problem-riddled Giro campaign is in tatters.

Contador crosses the line, and soon after a suffering Aru. Kiryienka is confirmed as the stage winner, while in second Spaniard Luis Leon Sanchez (Astana) at 12s, followed by Contador in third at 14s. Aru is 29th at 3m 1s. Porte is 55th at 4m 20s.

There is not one cheer or fist pump among the Sky riders and staff in Hotel Diana.

Instead, they stand gradually in ones, twos and threes to leave for their next hotel.

All are sharing the harsh reality that despite the consolation of a second stage (Italian sprinter Elia Viviani won stage 2) what they had set out and planned to do for months – to help Porte try and win overall - was as good as over.

With a brutal last week in the Dolomites and Alps before Sunday's finish in Milan to come, Porte was still 17th overall, but now at 8m 52s to Contador whose lead was 19s over Aru going into stage 15.

Realising the contrast of emotion that has just unfolded before us after his teammate's victory, Porte tells Fairfax Media and another reporter: "It's bitter sweet with Kiryienkya doing so well there."

He then reveals that he may have to quit the Giro to heal from his wounds. While it was a decision not made on Sunday morning, initial concern was that continuing to race in the mountains to come this week might hinder Porte's recovery and preparation for July's Tour de France.

Porte still can't believe his misfortune after starting the Giro as a race favourite.

He was penalised two minutes for taking an illegal wheel change from Australian Simon Clarke (Orica-GreenEDGE ) after puncturing on stage 10 and finishing 47s behind Contador, and then lost 2m 8s in Friday's stage after his crash. And now this ...

"I don't think it's a mental thing at all. I know it's not that," says Porte quietly.

"I was prepared for a fight. If anything the last few days made me want to fight harder."

To Porte's credit, he saw a positive, saying: "I came in as good as condition as I could.

"I was motivated as ever. It was a massive opportunity, but it hasn't worked out.

"But now I know what I need to do physically and mentally to prepare for this race."

Reminded that winning a grand tour like the Giro needs a little luck too, Porte summons up a smile and replies: "Yeah ... it sure does. You need to be lucky 21 days in a row don't you."

On that note, Porte is beckoned to an awaiting team car for the drive to their next hotel where that night, with team principal David Brailsford and coach Tim Kerrison, his next step would be planned.

That step was to get back on his bike on Sunday and continue ...

Rupert Guinness is covering the Giro d'Italia as a guest of Eurosport. Eurosport is covering every stage of the Giro live up until its finish in Milan on Sunday, May 31.