Jason Lezak threw a star-spangled spanner in the works of the much-hyped Ian Thorpe-Michael Klim showdown at the World Cup shortcourse meet in Melbourne on Sunday night.

American Lezak won the 50m freestyle, leaving third-placed Klim and fifth-placed Thorpe trailing in his wake at the Melbourne Sports and Aquatic Centre.

World championship relay gold medallist Lezak clocked a slick 21.68sec to beat Australian Ashley Callus (21.88), with Klim third in a time far slower than the sizzler he clocked in the morning's heats.

Klim, who clocked a personal best 21.86sec in the morning, was not overly disappointed with his bronze medal placing in 22.11sec.

The Victorian said he was just relieved the shoulder and back problems which had kept him out of action for the past 14 months appeared to be cured.

"This is just one step ahead to getting myself right for the selection trials (in March)," Klim said.

"Definitely this meet was a success - especially this morning's swim. A goal ticked off, so to speak."

Thorpe, who had been battling a virus which kept him out of the first two days of the meet, swam a creditable 22.41 despite still feeling the effects of diarrhoea and stomach cramps which left him bed-ridden on Friday.

"He's still got stomach problems but he swam okay this morning," Thorpe's coach Tracey Menzies said.

"He's still not over it but we thought he'd get in, have a paddle and see how we go."

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