Porte crashed on Friday on the wet roads of Jesolo and lost time in both the time trial and yesterday's first big summit finish to Madonna di Campiglio. Today he pulled the plug on a frustrating two weeks.
The teams woke up this morning for a rest day, but Porte is expected to travel home to his base in Monaco.
"I fell heavily on my knee and hip which caused me a lot of pain on Saturday's time trail and yesterday's stage. I just wanted to keep trying and give it everything, but now the medical team have advised me not to continue," explained Porte.
"I'm gutted it's ended this way and that I can't stay and support Leo [König], Elia [Viviani] and the team in the last week. They've been outstanding every step of the way and to not be able to repay that is tough."
Sky's staff packed Porte's bikes and his items from the motorhome this morning at the sunny ski resort, where yesterday the 15th stage finished at 1715 metres.
Porte lost more than 27 minutes at the end of yesterday's summit finish, but did not stop to explain what happened. It is likely that his crash on the roads near Venice on Friday was a factor.
Porte fell on his left side and hurt his hip and knee. He fumbled with his bike and restarted on an oversized bike from team-mate Vasil Kiryienka. He lost 2-08 minutes.
It added to the 4-06 loss in the time trial the day before in Valdobbiadene and the puncture incident in Forlì. Porte took a wheel from rival and friend Simon Clarke (Orica-GreenEDGE) and finished the stage 47 seconds behind overall leader Alberto Contador (Tinkoff-Saxo) — but the jury added another two minutes because being assisted by a rider from another team contravenes UCI rules.
The time losses knocked Porte out of the classification. While Mikel Landa (Astana) celebrated the stage win on the podium yesterday, officials began to calculate the overall standings. Porte sat 27th overall at 35-57 minutes behind Contador.
"I've had a lot of back luck this week with the puncture and the time penalty, but it was the crash on Friday that has taken its toll," Porte said.
"The plan for me now is to take some time off the bike, get the medical treatment that I need and reset my goals for the rest of the season and come back fighting. Hopefully I can get myself ready for the Tour team."
Porte has five weeks until the Tour de France begins on July 4 in Utrecht, The Netherlands. If recovered, he should be Chris Froome's right-hand man.
Czech Leopold König, who placed seventh in the Tour last year for NetApp, will now lead team Sky in the Giro. He sits fifth overall at 6-36.
Thank you for reading 20 articles this month* Join now for unlimited access
Enjoy your first month for just £1 / $1 / €1
*Read 5 free articles per month without a subscription
Join now for unlimited access
Try first month for just £1 / $1 / €1