There will be no Mack Horton-Sun Yang showdown in the men's 1500m freestyle final at the world championships.
Sun of China was a notable absentee at the world championships on Saturday after he failed to start his men's 1500m freestyle heat at the Duna Arena.
Although the 25-year-old trained in the pool on Saturday morning and is expected to compete in the men's 4x100m medley on Sunday, the Chinese Swimming Association confirmed his decision to sit out the 1500m race.
"Sun competed in several events with high intensity here during the past day. For the sake of his health and preparations for the Tokyo Olympic Games, Sun has decided to withdraw from the 1500m contest here," the Chinese Swimming Association said in a statement.
Sun's bid for a clean sweep of freestyle distance titles ended when he was beaten out of the medals in the 800m freestyle.
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Saturday's withdrawal means that Sun, the London 2012 champion, has now failed to contest the last three global 1500m freestyle finals.
At the 2015 championships he was a shock withdrawal on medical grounds minutes before the final.
At the Rio Olympics, where Horton famously called Sun a drug cheat, the Chinese swimmer failed to qualify for the medal race.
Horton qualified seventh for Sunday's final, clocking 14 minutes 59.24 seconds.
Ukraine's Mykhailo Romanchuk posted the fastest time with 14:44.11.
