Cowboys captain Johnathan Thurston.

North Queensland coach Paul Green and captain Johnathan Thurston blamed the poor completion rate in the second half of Thursday night's 20-12 loss to Wests Tigers on players trying too hard.

Trailing just 8-6 at halftime, the Cowboys never gave themselves a chance in the second term as they completed just eight of their first 16 sets of possession.

At one stage, North Queensland's second-half completion rate was just 38 per cent and it was their senior players, including Thurston, who came up with handling errors in key moments of the game.

A Thurston knock-on at dummy half just metres from his own line led to Tigers winger David Nofoaluma scoring from a 48th-minute scrum, while centre Esan Marsters crossed for the match-winning try in the 70th minute after a Lachlan Coote fumble in similar field position.

Test prop Matt Scott also lost the ball at a crucial period, while New Zealand World Cup five-eighth Te Maire Martin knocked on at dummy half and former Queensland Origin centre Justin O'Neill produced two handling errors.

"They are simple errors and they are the more experienced guys, but again they are probably the guys determined to try and lead us out of the slump," Green said.

"We put a lot of energy into playing well tonight and I think we were in too much of a hurry. We are trying a bit too hard. That was the case in the second half.

"We have to relax a bit, trust our game and be prepared to build pressure...but we weren't able to do that tonight, in that second half, in particular."

In comparison, the Tigers completed 20 of their 22 second half sets with the ball and a disappointed Thurston agreed with Green that it was impossible to win games when there is a such a contrast in the possession stakes.

"We'd just see an opportunity and try to capitalise on, and they (Tigers) would force an error and we would be on the back foot again," Thurston said "We didn't even complete at 50 per cent in the second half. It doesn't matter who you play.

"We defended extremely well for the amount of ball we coughed up, but it is just taking too much energy away and you can't compete."

The Cowboys lost forward Shaun Fenson with a dislocated elbow but Green said he wasn't expected to miss any games.