Sir Bradley Wiggins has been withdrawn from the Giro d'Italia due to a chest infection.
Team Sky medical staff monitored the 33-year-old Briton overnight following a difficult stage 12 that saw him slip off the back of the peloton in the closing stages and lose over three minutes to his rivals.
With his condition not improving, the decision was taken for Wiggins not to start the race's 13th stage from Busseto to Cherasco on Friday, with heavy rain once again expected.
Team Sky will now ride in support of Rigoberto Uran. The Colombian currently sits in third place overall, 2min 4sec off race leader Vincenzo Nibali.
Principal Sir Dave Brailsford told teamsky.com: "We monitored Bradley overnight and this morning we have withdrawn him from the Giro after consulting the team doctor.
"His chest infection has been getting worse and our primary concern is always the health of our riders.
Returning to UK
"Bradley will return to the UK today for treatment and to rest and we hope to have him back on the road as soon as possible.
"As a passionate racer he wanted to continue, but he is simply unable to do so on medical grounds."
Wiggins had fallen to 13th in the general classification, 5min 22sec behind Nibali, after his struggles on stage 12.
Defending champion Ryder Hesjedal has also abandoned the race. The Canadian had been lying 38th, more than 32 minutes adrift of the lead.
He said: "It is heartbreaking. I want to be here for my team and for all the people who have supported me to get me here to this point.
"I built my entire season around the Giro and I came here feeling great, but I have been suffering since the time trial [on stage eight].
"We are working on it, but we are not sure what is wrong. There is a virus that has been going around, so it could be that, or severe allergies, or going too deep on the TT combined with both. Whatever it is, I am only getting worse."