Johnathan Thurston turns heads as he sports speedos emblazoned with Karl Stefanovic's face on his CROTCH

NRL great Johnathan Thurston set tongues wagging when he took part in the Celebrity Relay Race at the Australian Swimming Trials in Brisbane on Wednesday.

Fans were shocked as the 41-year-old footy champ stripped off and approached the blocks in a pair of tight speedos which sported the image of Nine's Karl Stefanovic.

Johnathan grinned as onlookers gasped at his swimwear which featured the Today shows host's face printed across the crotch area.

Karl, 49, who was also taking part in the event, appeared to take Johnathan's cheeky stunt in his stride.

The breakfast TV star was seen to grin as he took his place poolside dressed in a  black swimsuit which he paired with a white skull cap and blue goggles.

NRL great Johnathan Thurston set tongues wagging when he took part in the Celebrity Relay Race at the Australian Swimming Trials in Brisbane on Wednesday. Pictured

NRL great Johnathan Thurston set tongues wagging when he took part in the Celebrity Relay Race at the Australian Swimming Trials in Brisbane on Wednesday. Pictured

Fans were shocked as the 41-year-old footy champ stripped off and approached the blocks in a pair of tight speedos which sported the image of Nine's Karl Stefanovic (Pictured)

Fans were shocked as the 41-year-old footy champ stripped off and approached the blocks in a pair of tight speedos which sported the image of Nine's Karl Stefanovic (Pictured)

The pair hit the water in the first leg of the Celebrity Relay Race which was part of the Australian Swimming Trials telecast by Nine on Wednesday.

Karl's relay team consisted of Beach Volley Ball gold medallist Kerri Pottharst and Olympic swimming great and two-time gold medalist Susie O'Neill.

Interviewed after the race Karl admitted his form could have been better. 

'It was really disappointing, I trained so hard for this race,' joked Karl in a Channel Nine post-mortem of the charity event.

Karl, 49, who was also taking part in the event, appeared to take Jonathan's cheeky stunt in his stride. (Pictured)

Karl, 49, who was also taking part in the event, appeared to take Jonathan's cheeky stunt in his stride. (Pictured)

'I nearly passed out,' he added.

Meanwhile, Johnathan admitted he was pushed to the limit by the swim.

'I’m pretty cooked at the moment, he told The Brisbane Times. 'Only 50 metres, and that’s all I had in me too.'

Also taking part in the 50 metre freestyle relay were Nova's Clint Stanaway, famed Aussie jockey Sylvia Jeffreys and Wallaby rugby champ Drew Mitchell.

The Block's  Darren Palmer also headed up a team consisting Today presenter Dan Antsey and Swimming Australia CEO Rob Woodhouse.