Melbourne Storm coach Craig Bellamy believes Billy Slater is getting back to his game-breaking best, just in time for their NRL preliminary final against Manly.

Slater was devastating in the Storm's qualifying final victory against Souths and instrumental in their rampant first half attack.

He showed his big-match temperament by assisting in three tries - including a 65m break to set up the first - and also scored one of his own.

It was no co-incidence the Storm's mid-season flat spot came at the same time when Slater was battling to overcome his serious knee injury, suffered in State of Origin II.

But Bellamy said the 28-year-old fullback was showing signs of returning to peak form with his blistering acceleration again on show.

After getting the better of Souths big gun Greg Inglis, his battle with Manly fullback Brett Stewart will be worth the price of admission alone.

"There were some really good signs there against Souths," said Bellamy on Monday ahead of their Friday night clash with Manly at AAMI Park.

"Obviously he performs well consistently every week but in big games he comes to the fore."

Bellamy said the Test custodian's involvement - he made five tackle breaks and 11 tackles against Souths - showed his value to the side.

"In a game like that to have that many involvements ... you'd like to think he's getting really close to his best."

- AAP