Manly's early NRL season woes have been compounded with star fullback Brett Stewart ruled out for the year following an operation on his left knee.

Stewart had hoped to return to the field by round 20 but the 25-year-old was told after surgery on Wednesday he would not be able to play again this season.

"It was a shock to Brett and to the entire club but he is a fighter and he will be back as good as ever," said Manly coach Des Hasler.

"The operation went well and Brett will make a full recovery but it won't be this season that's certain and we now have to get on with the rest of the season without him.

"The players accept that and will respond to the challenge as they did without him last year," Hasler said.

Stewart suffered the injury in round one when making a last-ditch tackle on Lote Tuqiri in Manly's 26-22 defeat by Wests Tigers.

Stewart suffered a similar injury to his right knee in round six of the premiership last season and returned in round 25.

The latest setback ends a miserable week for winless Manly and for Stewart who was told on Monday he must face a jury trial over claims he sexually assaulted a 17-year-old girl after the Sydney club's 2009 season launch party.

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