Melbourne NRL halfback Cooper Cronk might have seen the up-side to groin surgery which restricted him to pool work as other Test teammates returned to the training paddock.

Temperatures reached 40-plus degrees in Melbourne on Monday as Cronk and other Four Nations representatives Cameron Smith, Billy Slater, Greg Inglis, Adam Blair and Jeff Lima joined pre-season training for the first time.

Cronk underwent surgery in December upon his return from the UK, as did prop Brett White (shoulder), while fellow forward Ryan Tandy also had shoulder surgery following the Storm's grand final triumph over Parramatta.

Integral to Melbourne's success, Cronk may miss the start of the NRL season, although he will do his best to ensure that isn't the case.

"It's coming along good and I'm starting to do a little more free-moving now," he said.

"I should be able to start doing a bit of bike but just doing a lot of swimming at the moment.

"I can't run for another month ... it's going to be a while doing a bit of cardio work on the bike and the rower."

Renowned at the club for his diligence about injury rehabilitation, Cronk didn't miss a game last season.

"It sucks, to be honest, but it's just what happens sometimes," he said of the injury.

"I've had the injury for about two years but it was manageable, but going away overseas it became the sorest it had been."

Cronk had no regrets about delaying the surgery so he could be part of the Kangaroos' successful Four Nations campaign.

"To be part of a Kangaroos touring party is something that's held in high regard," he said.

"I've got a bit of hard work ahead of me from here on in but I definitely enjoyed my time over there."

He will remain in Melbourne while his teammates travel to the UK for the World Club Challenge on February 28, where they will take on Leeds for the second time in three years.

They lost the previous encounter 11-4, while Manly overcame the Rhinos 28-20 in 2009.

Luke Kelly, who was part of the Storm's title-winning under-20 line-up, may take Cronk's position while veteran Brett Finch could also fill the role.

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