Richie Porte says a chest infection has ruined his chances of challenging for Tour de France glory.
Porte, the default leader of Team Sky after Chris Froome pulled out injured on day five, was second overall after 12 stages and was expected to be the closest challenger to Vincenzo Nibali.
But bad days on the 13th and 14th stages have left him 13 minutes and 40 seconds adrift, with his inability to stay the course in the Alps on Friday particularly striking.
The Australian says his breathing has been inhibited, though.
"I have not been feeling 100 per cent so I went on antibiotics to try and knock the infection on the head," Porte told teamsky.com. "I have been feeling it on my lungs and I haven't been breathing well.
"All the guys have been riding so strongly for me, but this bug has really taken it out of me. It's just one of those things unfortunately."
Porte says he is feeling his struggles all the more knowing that he was Sky's main man with Froome out and Sir Bradley Wiggins not selected.
"It's really disappointing, especially as this was my first real chance to show what I could do in the Tour," he added.
"I'm going to take things day by day but I really want to complete the Tour and hopefully I'll be able to make it to Paris."