Australia's great Olympic swimming hope James "The Missile" Magnussen was Monday struck by a chest infection which ruled him out of a three-day training camp with his teammates.
The world 100m freestyle champion is due to spearhead the squad in London as Australia attempt to retain a position among the world's top two swimming nations alongside the United States.
Swim coach Leigh Nugent played down the illness concerns, insisting it was just a blip in his preparations.
"James has got a bit of a lung infection and he's had a bit of a problem with that before, but he's okay," Nugent told reporters.
"We all have some physical weakness in our make-up and when you're a bit stressed, it usually manifests in that area -- James' seems to be his chest.
"So it does seem to be an area of weakness for him. But you can have short periods of illness and that's pretty normal for a high-performing athlete."
It means he will miss a three-day training camp with his teammates in Canberra this week.
Magnussen is bidding to become the first Australian man to win the 100m freestyle Olympic gold medal since Michael Wenden in Mexico in 1968. He is also targeting the 100m world record in London.