Billy Slater might not return to NRL action until next month as his knee injury is proving frustratingly slow to recover.

The champion fullback was left out of ladder-leader Melbourne’s line-up for Saturday night’s clash with Parramatta and remains doubtful for the round-21 clash with St George Illawarra.

Coach Craig Bellamy said on Wednesday he wouldn’t rush his Test custodian despite the Storm’s recent form slump and didn’t know when he would return from the injury suffered in the second State of Origin match on June 13.

“I’ve heard he’s going to be back the last two weeks,” said Bellamy.

“I’m not holding my breath.

“I’ve told them (medical staff) not to tell me when they think he might be back – tell me when he’s back.”

Slater was initially given a four to six-week prognosis after injuring his knee.

Bellamy said Slater was running but the issue was with his agility and the angles he runs.

“Because of the way he runs and his agility, it’s a bit more serious for players who have that in their game, more so than bigger players who mostly run straight lines.”

“He’s got a lot of footy ahead this season and in the years to come so we’re not going to risk it.”

He admitted that as well as Slater’s zip in attack, the Storm missed his organisation and the confidence he gave the team in defence.

Regular five-eighth Gareth Widdop has again been named at fullback to face the Eels with Bellamy rating him as one of their best despite their run of three successive losses.

Rory Kostjasyn will wear the No.6 jersey while high-flying winger Matt Duffie, who is out for up to six weeks with a shoulder injury, has been replaced in the starting line-up by Sisa Waqa.

Centre Dane Nielsen, who missed their last-round loss to the Cowboys with a biceps injury, is set to return.

Representative halfback Cooper Cronk was again rested from training but has been named to play the Eels at Parramatta Stadium.

Bellamy says Parramatta, who are running last, would be up for the challenge under their coach, former Storm player Stephen Kearney.

“They’re a side who, over the last few weeks, have slowly and surely improved.

“Steve will have them pumped up and it should be a good clash.”