Munster has been battling to overcome a knee injury. In Round 24, he suffered a cut to the knee during a loss against the Parramatta Eels.
That then became infected, with Munster saying himself earlier this week that it was a 50-50 call on whether he'd be able to play or not, while also admitting he ran the risk of a longer stint out if things became worse by playing.
"It's a bit of a healing process. I can still play on Friday, but they can't guarantee the stitches will hold up," Munster told the club website on Monday.
"It's a 50-50 call between me and the coaching staff.
"We could win, open it up, have the week off and who knows, I could be back to square one. But if I play, open it up and we lose and then I've got to try back up the following week so it's a tough situation we are in."
Cameron Munster trained for the Storm today. Craig Bellamy saying the decision on whether he'll face Manly is up to him. #NRLStormSeaEagles
— Ed Chisholm (@ChisholmEd) September 9, 2021
"It's not so much he's got a knee injury, it's more that it's been split open," Bellamy said.
"He's had stitches internally, stitches on the outside and they're just worried about it opening up.
"It's basically up to Cameron really, how comfortable he feels, whether it's going to effect him too much.
"He's done most of the training today so we'll just see how he pulls up but he got around the field OK today. Basically the decision's up to him."
If Munster is ruled out, it's anticipated Nicho Hynes would come back into the starting side. The winner of their clash with the fourth-placed Sea Eagles will advance straight to the preliminary finals, while the loser will face a sudden-death semi-final next weekend.