Ian Thorpe said he felt flat on his return to major competition at Australia's Commonwealth Games swimming trials here on Tuesday.
Australia's most decorated Olympian with five gold medals had his first major swim in 17 months following his triumphant Athens Olympic campaign in which he won two gold medals.
Thorpe, 23, has given up the 400m freestyle event for which he is the reigning Olympic champion to concentrate on the 100m and 200m freestyle events ahead of the 2008 Beijing Olympics.
He easily won the 200m freestyle at the trials on Tuesday swimming 1:46.42, some 2.38secs ahead of his nearest rival, but was disappointed with his swim.
His time was well outside his world record time of 1:44.06 set at the Fukuoka world championships in Japan in 2001.
Thorpe said he wasn't ill, but felt lethargic.
"I just felt a bit flat ... but I think I'll be alright for the next day," he said.
"I'm in a strange (new) pool and it's been a different preparation for me. I felt under no pressure coming in, I felt pretty relaxed, the most relaxed I've been for at least five years."
Thorpe has been reported as saying he intends to retire from competitive swimming, at the age of 25, after the Beijing Games.
{{/usCountry}}Thorpe has been reported as saying he intends to retire from competitive swimming, at the age of 25, after the Beijing Games.
{{/usCountry}}He said a new seven-year, multi-million-dollar deal with sportswear company Adidas was unlikely to mean he would extend his career to the London 2012 Games.
"It's not out of the question, but at the moment I intend to retire in Beijing," Thorpe said.
Thorpe became Australia's most successful Olympic athlete when he added two gold, one silver and one bronze medal at the 2004 Athens Olympics.
Thorpe also won gold in the 400m and the 4x100m and 4x200m freestyle relays at the 2000 Sydney Olympics.
He also has won 11 gold medals at three world championships.