Melbourne Storm coach Craig Bellamy has revealed he doesn't know when Ryan Papenhuyzen will be back on the field.

The star fullback shattered his knee during the final weeks of the 2022 regular season, ending his campaign, and while it was tipped he would be back on the park for Round 1 this season, his recovery has been slow.

Papenhuyzen travelled to the United States of America in January to work with renowned physiotherapist Bill Knowles, where he revealed one of the key learnings was to not rush back onto the park.

That all but ended his chances of playing in Round 1, with the club then suggesting he could be back as soon as Round 6.

Papenhuyzen himself then labelled that as "ambitious", with something later in the season deemed more appropriate for the star fullback, who was in the State of Origin picture last year on the back of incredible form.

Speaking on NRL 360 though, coach Craig Bellamy revealed he has no idea when Papenhuyzen will be back on the park.

“I'd love to be able to tell you guys that, but I honestly don't really know,” Bellamy said.

“It has obviously been a lot slower than what everyone thought, obviously Paps (Papenhuyzen) has been over in the states to work with a guru guy over there.

“Still coming along really slowly, he hasn't started any running on land yet he's just still running in the water, so they're not sure how long it is going to take.

“It's been hard for Paps, this slow recovery and not knowing when he can get back in the game.

“We just need to be patient and hope that when he starts running it improves quickly, but at this stage he's still a fair way away from doing any training with the team.”

Bellamy still suggested the best scenario would be Round 6, but revealed that the thought Papenhuyzen wouldn't play all season had crossed people's minds.

“Yeah, again that thought has probably passed over a few people's minds,” Bellamy said.

“But we are confident, if we stay patient and Paps does the work he needs to do and our medical team get it right, he'll be back at some stage.

“Best scenario, six to eight weeks, maybe 10 weeks, but there's no guarantees there.

“We certainly aren't going to push him and take any chances.”

Papenhuyzen has struggled with injury over the last two seasons, with a concussion writing off much of his 2021 season following a sickening hit.

The star fullback, who was born in Kellyville, has played 69 games for the Storm since his 2019 debut, but managed just 15 games in 2021, and 12 in 2022.

In his absence, winger Nick Meaney will start the year at fullback, while more backline issues could pave the way for a debut to Will Warbrick on the wing in Round 1, when the Storm open the season on Thursday evening with a clash against the Parramatta Eels at CommBank Stadium.