Movistar's English cyclist Alex Dowsett has been forced to postpone his attempt at the world hour record after failing to recover from a broken collarbone.
The 26-year-old suffered the injury in training last week and had been expected to announce his record attempt was off as a result.
"I'm really gutted this has happened," Dowsett said in a statement today.
"I've never worked harder for anything and to make this difficult decision with the team and lose this opportunity is a real blow. The positive is that it is a record attempt so we will be attempting it at a later date.
"I'd like to thank everyone that's supported me with words of encouragement both in training pre-crash and words of support and well wishes post-crash, it really was overwhelming. I'll now recover properly and be back to full fitness for the road season and another crack at the 'perfect hour.'"
The world hour record is currently held by German rider Matthias Brandle.