British triathlete Alistair Brownlee will have surgery on a persistent ankle injury on Wednesday.
It puts the Olympic champion's bid to qualify for the Rio 2016 Games on hold.
The 27-year-old world and European champion could still clinch his Olympic place at an assessment race in 2016.
"My left ankle has been giving me bother since 2013, with a range of different niggles," he said. "Getting it sorted gives me the best chance of being 100% for next season."
The injury has troubled Brownlee from the start of the season.
It forced him to miss World Triathlon Series (WTS) races in Abu Dhabi, Auckland and Gold Coast.
It flared up again at the Rio test event this month, causing him to pull out of competition in Stockholm at the weekend.
British Triathlon criteria for Olympic qualification is to finish in the top three in the Rio test race and also on the podium in September's WTS Grand Final in Chicago.
Brownlee's younger brother Jonny, 25, is out until next month with a stress fracture to his left leg.
The Yorkshire-based Brownlees came first and third in the London Olympic triathlon in 2012.