When it rains in Townsville it generally pours - and doesn't Cowboys coach Graham Murray know it.

Without a win and up against premiership powerhouse Parramatta on Saturday night, the Cowboys have now lost Matt Bowen to a knee injury.

"I'm not sure of the actual medical terminology, but his knee's sore and he's had a cortisone injection this week," Murray said.

"The specialist doesn't want him to play so we'll give him a week's rest and hopefully it will settle down for the following week.

"He's been carrying a little niggle for few weeks now and it just hasn't settle down like we thought it would.

"He's just gone to the doctor this week and the doctor's advised to give him a week off."

It couldn't have come at a worse time for Murray and the Cowboys, who have struggled to put points on the board over the opening three rounds.

They managed just a solitary penalty goal against Brisbane last Friday night and have averaged just 10 points a game.

Star halfback Johnathan Thurston has struggled to get into the swing of things following off-season shoulder surgery, Murray admitting on Thursday the knee injury Bowen had been carrying over the opening few weeks had also proved a hindrance.

"Matty's been down, he hasn't been happy the way he's playing and that's probably got a bit to do with it," Murray said.

"Matty's one of our most important players but at the same time we don't want to put his knee at risk either."

Murray said either Obe Geia or John Williams would come into the squad at fullback.

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