Injured Newcastle superstar Andrew Johns has been cleared to play in Saturday night's NRL match against St George Illawarra, but that wasn't enough for some bookmakers to reopen betting on the WIN Stadium clash.

Johns, who has been struggling with a neck injury that kept him out of last Sunday's 26-22 loss to the New Zealand Warriors, trained strongly with his Knights teammates in Newcastle before boarding the team bus for Wollongong.

His management company issued a release claiming the champion No.7 would be right to tackle the Dragons, but Centrebet's Gerard Daffy said betting on the clash would remain suspended until he was certain that Johns would in fact play.

"There is a major difference between being cleared to play and playing," Daffy said.

"At some point in time they're going to have to say `yeah he will play or no he won't', which I assume is going to be tomorrow morning.

"I don't know what to do. If it's spasms in his neck, I'd be very surprised if he'd be playing anyway."

It's a case of once bitten, twice shy for bookmakers, who were last week stung with big bets on the Warriors before news of Johns' unavailability became public.

Johns initially hurt his neck during a weights session on Thursday, but was not ruled out of the game against the Warriors until late Sunday morning.

TAB Sportsbet's Glen Munsie reopened his market in the afternoon following news that Johns had come through the morning session unscathed, but admitted there was no guarantee that he would play.

"After the training session he appeared to be as good as gold," Munsie said.

"We think he'll play, but of course he goes to bed tonight and wakes up with a pain in his neck he mightn't play, but at this stage he'll be playing."

Newcastle coach Michael Hagan appeared in little doubt that his prize playmaker would take to the field against the Dragons.

Johns travelled to Sydney on Thursday to see spinal specialist Professor John Yeo, who treated the halfback three years ago for a protruding disc in his cervical spine.

Professor Yeo said he was satisfied that Johns' neck problem was muscular and unrelated to his previous neck injury, with the Knights playmaker completing a rigorous session before receiving a final clearance from Newcastle doctor Neil Halpin.

"It was good to know it wasn't a serious injury and it was only a week, which is what we hoped for," Hagan said.

"We've probably made other plans assuming that he may have been out for another week or two, but we don't have to worry about those plans anymore which is good."

Dragons coach Nathan Brown said he hadn't let speculation over Johns' availability affect his side's preparation this week, but admitted his presence would have a large bearing on the result.

Statistics would seem to back him up, with Newcastle's winning rate since 2003 at 30.8 per cent without Johns, while it climbs to just over 60 per cent when the 31-year-old does play.

"We've never suspected that he wouldn't play (but) we haven't really talked about Joey playing or not playing," Brown said.

"Obviously if he doesn't play, regardless of what anyone would like to say, it makes the contest, attitude wise and physically, just as hard.

"But there's probably just that little bit less threat, because Joey's the world's greatest player probably to ever play the game."

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