Billy Slater watches on from the bench in his return game.

Billy Slater promises long-time teammate Cooper Cronk's announcement to move to Sydney at the end of the season will have no impact on his own playing future at the Melbourne Storm.

The 33-year-old is focused on returning to his superstar form after making his comeback from two long injury-plagued years.

"(Cronk's decision) is a totally separate issue to me," Slater said. "This won't determine what I'll do next year and I haven’t really thought about that. 

"I've been lucky to be down here for 15 years now. I've brought up a young family down here.

"I'm just enjoying playing football again. I've had three games under my belt now and hopefully I'll get many more before I have to make that decision."

In his return, Slater has helped the Storm to a perfect 5-0 record to start the season, and his early form has fueled possible selection in the upcoming Anzac Test.

"I feel I'm at the level but I'd like to play a few more games before I make some decisions," Slater said. "At the end of the day, it's not my decision to make.

"I'm happy with where I'm at performance wise. I'm happy with where my shoulder's at and where my game's heading. 

"I'm building and getting that match fitness after not playing much footy in two years."

Slater has an ideal opportunity to impress selectors in Melbourne's grand final rematch with the Cronulla Sharks this Sunday at AAMI Park.

While he missed last year's premiership decider, it was still difficult for Slater to stomach.

"(This week's) a little less emotional for me (but) I was still part of the club last year and it was a tough loss," Slater said. " I know it's a grand final replay. It's going to be a huge occasion here.

"They're a tough gritty side. Any team with Luke Lewis, James Maloney and Paul Gallen, they're always going to come at you and be really physical. 

"They didn’t win the comp for no reason last year."

Despite remaining the NRL's only unbeaten side, Craig Bellamy's side is motivated to further improve. While their defensive effort has singlehandedly won their first five matches, they're intending not to need to rely on their defence.

Their uncharacteristic error-riddled performances have Melbourne's coaching staff puzzled and without explanation.

"If you find out let us know," Slater said. "Our coaching staff is banging their heads trying to figure out why we're dropping the ball like we are. 

"We're trying things as well and expanding our attack. Whenever you're pushing the limits and trying to get the best out of yourself, you're going to come up with a few errors but we'd like a few less.

"It'll be a big test for us (against the Sharks). We haven’t played to the best of our ability in the last few weeks. We're certainly going to have be near that level on Sunday."