BUSSETO, Italy (AP) -- Tour de France champion Bradley Wiggins and defending champion Ryder Hesjedal both withdrew from the Giro d'Italia before the start of Friday's 13th stage.
Team Sky said that Wiggins made his decision on the advice of the team physician because of "a worsening chest infection."
"We monitored Bradley overnight and this morning we've withdrawn him from the Giro after consulting the team doctor," Team Sky general manager Dave Brailsford said. "His chest infection has been getting worse and our primary concern is always the health of our riders. 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."
Wiggins struggled throughout the Giro, both on rainy descents and on steep climbs. He lost more than three minutes in Thursday's rainy stage and left the race in 13th place, 5 minutes, 22 seconds behind overall leader Vincenzo Nibali.
"As a passionate racer he wanted to continue but he is simply unable to do so on medical grounds," Brailsford said.
Sky still has Colombian rider Rigoberto Uran in third place overall, 2:04 behind Nibali, who holds a 41-second lead over 2011 Tour winner Cadel Evans.
Wiggins is expected to help teammate Chris Froome at the Tour this year but he said before leaving for Italy that he might grab the team leadership in France himself and try to defend his title. That prompted Sky to issue a statement saying that Froome will be the team leader for the French race.
In last year's Tour, Froome finished runner-up to Wiggins.
The Garmin-Sharp team said that Hesjedal, who was more than 32 minutes behind in 38th, withdrew because of a "deteriorating physical condition."
The Canadian has been struggling with power since the Stage 8 time trial.
"It's heartbreaking," Hesjedal said. "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 TT. We're working on it, but we're not sure what's wrong. There's a virus that's been going around, so it could be that, or severe allergies, or going too deep on the TT combined with both."
Stage 13 on Friday is the race's longest, a mostly flat 254-kilometer (158-mile) leg from Busseto to Cherasco, with a few hills shortly before the finish.
The race hits the mountains again over the weekend, with Saturday's stage climbing Sestriere and Bardonecchia and Sunday taking riders into France and up the Col du Galibier, which is often included in the Tour.
The race ends May 26 in Brescia.