A stomach bug may have struck down Johnathan Thurston but a potential NRL top four finish has also lit a fire in the belly of the North Queensland co-captain.

Coach Neil Henry said on Friday Thurston would defy illness as the Cowboys vie for a home final with victory over lowly Cronulla in Townsville on Saturday night.

Thurston missed two days of training in the lead-up to the potentially crunch game along with the likes of backrower Gavin Cooper.

But Henry backed his playmaker to rise to the occasion as the Cowboys look to snap a worrying three-game losing run ahead of a rare NRL finals campaign.

Fifth-placed North Queensland can secure a top-four finish by relegating the Sharks to their seventh straight loss and knocking off the in-form Warriors on Saturday week.

Easier said than done with Thurston battling to take the field - unless you speak to Henry.

"He's had a bug and lying in bed all day," Henry said on Friday.

But he quickly added: "Hopefully he is much better.

"He started to eat solid food last night, he's nearly had two days off.

"Gavin Cooper is the same, but we expect them to be okay.

"With those things you get a bit of dehydration but it's normally gone within 24 to 48 hours - the doctor's not too worried about it."

But the Sharks should be with Thurston expected to run out on Saturday night.

The Cowboys playmaker is just five points shy of a personal point-scoring milestone.

He sits on 995 points and needs only five to register 1000 for his NRL career.

The 13th-placed Cronulla can leapfrog the Roosters and Panthers with two straight victories but few would be backing them after they led 25-18 with seven minutes left last weekend and still lost 36-25 to the Roosters.

While Henry is yet to finalise his 17 he gave the green light for teenage forward Jason Taumalolo to make his second NRL start this weekend.

Henry said the choice for the final bench spot would come down to Ashton Sims and Scott Bolton.

Sims is being troubled by a knee complaint despite playing all 22 games this season.

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