Five-time Olympic champion Ian Thorpe admitted he could not recall his race after finishing second on his return to competitive action in Singapore.
The Australian, 29, who quit the sport five years ago, clocked a time of 56.74 seconds to reach Friday's final of the 100m individual medley.
Thorpe said: "It's nice to get the first swim out of the way. I was a little bit nervous before.
"I can't remember the race. I don't know if it was any good or not."
Thorpe, who is bidding to swim at the 2012 Olympic Games in London, qualified sixth-fastest for the final at the Singapore World Cup.
He added: "I am glad I have another opportunity for a final.
"I'm sure when I watch the video there will be things I can work on. It is my first swim, I'm glad it's out of the way."
Colombia's Omar Pinzon, 22, who won the heat, said: "When he was retiring I was just starting to get into swimming seriously.
"It was exciting swimming next to him, we will see how the race (final) goes."
Thorpe's fellow Australian, triple Olympic champion Libby Trickett, also made her comeback in Singapore.
The 26-year-old was competing in her first international meet since the 2009 World Championships and qualified for the finals of the 100m butterfly and the 50m freestyle with the fifth-fastest times in both.
"I'm so happy to have made it through to the finals. I feel giddy and I know it's weird for a 26-year-old to feel giddy but it's true," said Trickett.
"I'm just so happy right now and I honestly have the best job in the world. While both swims hurt, I'm really looking forward to tonight.
IAN THORPE OLYMPIC MEDALS
Gold 200m freestyle, 2004
Gold 400m freestyle, 2004
Gold 400m freestyle, 2000
Gold 4x100m freestyle, 2000
Gold 4x200m freestyle, 2000
Silver 4x200m freestyle, 2004
Silver 200m freestyle, 2000
Silver 4x200m freestyle, 2000
Bronze 100m freestyle, 2004
