Melbourne Storm football director Frank Ponissi has backed Billy Slater to play on in 2018 but admits nothing can be certain until after Sunday's NRL grand final.

The 34-year-old full-back will play his 299th NRL game on Sunday and many at the Storm believe he will eventually decide to keep playing next season.

But he has refused to publicly make a decision leading into the game.

"Billy Slater has earned the right to be left alone, he has played 15 seasons and no one has asked him what he is doing," Ponissi said.

"We will give him the respect he deserves and if he decides after Sunday that he has had enough then, while we will be disappointed, we will respect his decision.

"But to be stuck on 299 games and 29 State of Origins, I have a feeling he will back up again but not just that I feel he is enjoying his football more than any other time."

Ponissi added the Storm selfishly hope Cooper Cronk retires rather than play for a Sydney club next season with the Storm wanting to secure him as a part-time backs coach in between his media commitments.

The Storm flew out for Sydney on Wednesday afternoon and face a day of media and promotions commitments on Thursday before completing their preparations for Sunday.

Both the Storm and North Queensland Cowboys are expected to name unchanged sides barring any last minute manoeuvres.

Ponissi admits the Storm were cheering on the Cowboys as they came from eighth place to make the preliminary final.

"For the first couple of weeks, to a degree, we were cheering for the Cowboys against St George and Cronulla," Ponissi said.

"Like anyone else you go for the underdog but it got into the preliminary final last week and we said we have to stop supporting them as we could be playing them next week.

"It has been a great story but they also have a pretty good team."

"If you look at their grand final team they have 14 of 17 players who have played in a grand final before and we only have 12 backing up from last year's team.

"They have an experienced team and one capable of winning a grand final on Sunday."

The "Cinderella" Cowboys will have plenty of neutral support against the minor premiers but it won't matter much to the Storm who have been second fiddle to Richmond's AFL grand final hysteria in Melbourne this week.

"Richmond is in their first AFL grand final in 37 years and they have a huge following. We expected that and we don't take that to heart," Ponissi said.

"We are getting daily coverage on radio and in the papers so everyone has been great. We understand our place.

"We expected most of the people to be following the Cowboys, they are the Cinderella story and the so-called underdogs, so Australians always love the underdogs and we understand that but we are expecting a big crowd from Melbourne and they will be vocal."

The Storm had former All Blacks captain Richie McCaw speak to them in the lead-up to last week's game but Ponissi said he wasn't planning on any special guests for this week's game.