Former Queensland and Australian halfback Mark Murray believes Brisbane can upset Manly with Matt Gillett at five-eighth - provided he doesn't try to play like Darren Lockyer.

Lockyer ended a suspenseful four days when he ruled himself out of Friday night's NRL preliminary final in Sydney on Wednesday morning.

Twenty-three year-old Gillett, who played Queensland Cup under Murray at Norths in 2009, faces the biggest challenge of his budding career filling in for Brisbane's match-winner.

But Murray is confident if he keeps his head, he will do the job.

"Matt is a footballer. If he plays like Matt Gillett and doesn't try to play like Darren Lockyer, he'll be fine," he told AAP after Lockyer gave up on his bid to play six days after having three metal plates inserted in his fractured left cheek.

"He played half the season at five-eighth for us (Norths) in 2009 and was very good.

"He was our player of the year.

"Defensively Brisbane will be stronger and he's a player who can do special things if the opportunity arises."

Murray, whose own playing career was cut short by an eye injury in the mid 1980s, played much of his representative football alongside Wally Lewis who also believes Gillett is a good choice to step in for Lockyer.

Murray said Lockyer had taken the pressure off everyone by making his decision early, allowing the team to focus on Manly and get settled.

"They can still win," said Murray who captained Norths to a premiership upset over a Souths side coached by Wayne Bennett in the 1980 Brisbane grand final.

"You can understand Darren wanting to play given the occasion and the sense of responsibility he feels," he said.

"But once you get past the emotion you can make a clear decision and Locky has done that."

Murray believes if Brisbane match Manly's physicality with and without the ball they have the the players to win the game, even without their inspirational skipper.

"Manly base their game on that physicality and Brisbane has to meet it head on to have a chance," he said.

Murray tipped Gillett would be a representative player and Brisbane's best forward within two years even before he made his NRL debut in 2010.

But he's also been greatly impressed by the progress of Gillett's teammate, Josh McGuire.

McGuire suffered a potentially career-threatening eye injury early in the season and since being given an opportunity by coach Anthony Griffin after representative prop Ben Hannant was injured, has continued to make a statement.

"Josh was given an opportunity by his coach to step up and he's close to the best prop in the competition," said Murray.

"The way their young players are performing is a real credit to their coach who's got them playing consistently good football."

Murray said Gillett, who fought his own injury battles this season, was starting to find his best form again.

"He was talked about at Origin time and he wouldn't look out of place in Australia's squad for the Four Nations," said Murray.

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