Papenhuyzen has not played since he fractured his kneecap in a sickening collision with Jack Wighton last July, and has since spent time in the US seeking treatment.
The reality of Papenhuyzen's recovery was laid bare on Tuesday, with Storm officials confirming the fullback was not on track to return until at least April.
"Paps continues to work hard on his rehab program, building strength in his right leg," the club said in a statement.
"If he continues to progress well, it's hoped he will return to the field around rounds six to eight."
The news means Papenhuyzen will endure a third straight season derailed by injuries, after concussions set him back in 2021, before last year's hamstring and knee problems.
The Storm will likely turn to Nick Meaney at fullback in Papenhuyzen's absence, with the gun No.1 set to miss headline clashes with Parramatta, South Sydney and the Sydney Roosters.
Papenhuyzen is one of several injury concerns for the Storm.
Centre Justin Olam is expected to miss the first month of the season with a fractured forearm suffered during last weekend's pre-season loss to the Roosters.
Fellow centre George Jennings is now unlikely to return until round four from last year's ACL rupture, while Marion Seve is also in doubt for the start of the season with a knee injury.
It is likely to leave Grant Anderson starting the season at centre, with rookie Jack Howarth another option to debut.
Melbourne also confirmed that recruit Tariq Sims had suffered a calf injury in the pre-season, but was some hope of being fit for the early rounds.
