North Queensland winger Antonio Winterstein is facing the prospect of being sidelined for the remainder of the NRL season after tearing his pectoral muscle in Saturday's 24-4 defeat by Manly at Brookvale Oval.

The New Zealander suffered the injury when vainly trying to stop Sea Eagles' centre Steve Matai scoring a try in the opening minutes of the second half and was forced off the field.

Winterstein, who joined the Cowboys from Brisbane at the start of the year, had battled back onto the field from a badly-broken jaw sustained during pre-season training and was hopeful rather than confident of returning to action.

"It's not too good. I just tried to hold (Matai) up and just stretched too far," Winterstein said.

"We won't know how bad it is until tomorrow after scans."

"I'm trying not to look that far and I'm hoping for the best that it's not too bad."

"It's just a burning sensation and there's no strength in it at the moment."

Cowboys coach Neil Henry was unhappy with the performances of the referees and slammed the decision to place former Sea Eagle Glenn Hall on report, after he caught Glenn Stewart across the face with a swinging arm.

He was also upset that a knock-on was not awarded against Matai in the build-up to Manly's second try scored by George Rose.

"I don't think Matai looked like he knocked it on. I think he did knock it on, so there you go, play on," he said.

"Glenn Hall gets clipped high in tackle and it's (ruled) falling into the tackle and he clips Stewart high and it's a penalty and placed on report. Anyway, you get those inconsistencies sometimes."

The defeat extended the Cowboys' wretched record when halfback Johnathan Thurston was unavailable for selection to just seven wins in 26 matches, since his arrival at the club from Canterbury in 2005.

Thurston and co-captain Matt Scott were absent due to State of Origin commitments, but Henry refused to make any excuses for his side's disappointing performance.

"I don't think many sides would have defended that flat kick from (Daly) Cherry-Evans for their first try and we should have defended our line better for the second try," Henry said.

"We were a bit flat and credit to them, they defended well."

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