The unbeaten Storm will tackle the winless Dragons at Jubilee Stadium without Dally M Medal-winning halfback Jahrome Hughes (hand) or goal-kicking centre Nick Meaney (facial fracture), who have both undergone surgery.
Papenhuyzen hurt his ankle late in their last-round victory over Penrith but didn't require any strapping and was moving freely in their final training session before flying to Sydney, with coach Craig Bellamy saying he was set to play.
"He (Papenhuyzen) hasn't done all of training this week but he's done a bit of it and he did the last session that we did and seemed to get through that OK, so if he gets through today he will be fine," Bellamy said on Friday.
Grant Anderson has also overcome a knee injury against the Panthers to take Meaney's No.4 jersey while gun utility Tyran Wishart will start at halfback for Hughes, who was a bystander at training although is only expected to miss a further match.
"It wasn't a great night ideal for us injury-wise, losing a couple of really important players to our team, but it's been a long turnaround so we've had plenty of time to get ready and hopefully we've used that time well," Bellamy said.
"Wish (Wishart) hasn't played a lot at that position with us so hopefully this week he's got a bit of a feel for the guys playing around him, and them for him."
Despite their contrasting results to open the season, Bellamy expects a tough tussle at Kogarah.
Coming off a round-three bye, the Dragons were in the hunt in both their matches, blowing a 24-12 lead to lose to third-placed Souths by a point in their last outing.
"They're a big side and they play at pace and they like to move the ball around, so it's always going to be hard to handle," Bellamy said.
"They've probably been a little bit unlucky both their games this year so ... every team in the competition has got their strengths.
"They're probably all still working out the best way to play their games but certainly with St George, moving the ball and offloading the ball, that's a really strong suit of theirs."
Meanwhile, Melbourne chief executive Justin Rodski confirmed the NRL had approved cap dispensation for medically-retired prop Christian Welch.
"Our request for cap relief has been approved in principle," Rodski told AAP. "We are still working through this with the NRL to determined date and amount of dispensation."
That will free up an additional six-figure sum for the Storm this year to help keep Wishart, who will become a free agent on November 1.
Bellamy rated 25-year-old Wishart as valuable as his star-studded spine.
"Without a doubt - he seems to be able to come on in any position at any time. He gets the job done," the coach said.
"That's really helpful to have a player in your squad that can do that."