Melbourne Storm star Cameron Munster has admitted that he is unlikely to feature in the club's opening game of the season as he slowly recovers from a groin issue that saw him miss both trial matches.

It is a massive loss for the Storm, who will take on the reigning premiers, the Penrith Panthers, as they chase their 22nd consecutive round one victory - a feat that has seen Craig Bellamy never lose in round one.

After Bellamy revealed that Munster is 'touch and go' on Saturday, Munster spoke to reporters ahead of the match, stating he won't play unless he is 80-100 per cent fit.

"I was looking good for the Fiji game, and then I slipped in the shower, so it wasn't ideal," Munster said.

"It's a frustrating injury, but I'm doing everything I can to get it right. I tried to do a little bit today, but I need to be 80 to 100 per cent to be able to play on Friday

"If I'm not right by Tuesday or Wednesday, I will pull the pin."

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While it was originally revealed that he had a calf injury after slipping in the shower, the five-eighth revealed it is actually a groin injury and sustained it after slipping in the shower and doing the splits.

Munster's likely unavailability for the game against the Panthers will likely see Jonah Pezet fill the vacant position after spending time there throughout training and during the pre-season trial matches.

Teammate and hooker Harry Grant praised the 21-year-old who has only played seven NRL games to date in his career.

"Pez (Pezet) has done a really good job of being patient and he could potentially be a starting player at a number of other clubs, but he committed to our club and wants to keep learning and keep developing his game," Grant said of Pezet via AAP.

"If he does get his opportunity I'm sure he will be ready to take it."