Five-time Olympic champion Ian Thorpe said it was "premature" to judge his comeback despite disappointing results at the Italian Winter Championships.
Thorpe finished 16th overall in the 100m freestyle and 10th in his first 200m freestyle in almost six years.
The 29-year-old Australian also struggled at last month's World Cup meets in Singapore, Beijing and Tokyo.
Speaking in Italy on Sunday, he said: "It's not a concern now. Maybe later, but now it's too premature."
Thorpe retired in 2006 but announced earlier this year that he was returning, with London 2012 the target.
After finishing well off the pace at the World Cup short-course meets in November, Thorpe made his long-course comeback in Italy over the weekend.
He finished in a time of 50.84 seconds in the 100m free and one minute, 51.51 seconds - seven seconds off his best time - in the 200m free. American star Ryan Lochte won the 200m in 1:44.44 at this year's world championships in Shanghai.
"I'm in training at the moment," Thorpe told The Australian newspaper. "I came here to take the opportunity to race, and to race against fast swimmers. I don't look at where I come in the race.
"I look at the time, how fast it is. I watch it, I critique my race after it but I have no control of what the others are doing."
Thorpe, who won 11 world titles and set 13 individual world records during the first part of his career, is focused on qualifying for the Australian team at the national Olympic trials in March, and insisted competitive racing would benefit him in the long run.
"It's important that I race, whether it's a good result or a bad result," he said. "I have to keep racing at this stage."
Thorpe will next compete at January's Victorian Championships in Australia.
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 4x100m medley, 2000
Bronze 100m freestyle, 2004