David Davies has withdrawn from Great Britain's 64-strong squad for this month's European Championships.
David Davies has had problems recovering from a foot infection
The 21-year-old Welshman had surgery on an infected foot in May and recovery has been slower than expected.
Coach Dave Haller confirmed that the 1500m specialist would miss the event in Budapest, Hungary, on 26 July although he has been invited to travel.
"David has missed too much training to consider racing in Budapest," Haller told SwimNews.
"If this was going to happen this was probably the best time. It's been good for him to have a bit of a rest. He'll bounce back and probably be better for it."
Davies, who has just returned to his Barry home from a training camp in Malta, will now aim to be back to his best in time for the World Championships in Melbourne next March.
There's an enormous gap between 1500m and 10km
Swimming coach Dave Haller
The Welshman won 1500m freestyle gold in the Commonwealth Games in Melbourne last March, adding to the Olympic bronze he claimed in Athens in 2004.
But Haller revealed that Davies is also considering entering the inaugural Olympic 10km open water marathon for the Beijing Olympics in 2008.
"Yes, we've looked at it, but he'll have to do a couple of 5km first to see how he gets on," Haller added.
"Our approach would be to start with the shorter events. Physiologically he's suited to it but there's an enormous gap between 1500m and 10km.
"It's a big decision to take on the 10km because we wouldn't want to throw away the 1500m and you might lose speed.
"If you go too far training for the sake of endurance, it would affect your speed in the pool."