KNIGHTS utility Matt Hilder will have CAT scans on his head today to hopefully solve the mystery neurological condition that kept him out of yesterday's 34-22 loss to Brisbane at EnergyAustralia Stadium.

Hilder suffered dizzy spells, numbness and tingling down his side and leg at home on Saturday night, then again when he arrived at the ground yesterday.

He was examined by Knights medical officers Peter McGeoch and Neil Halpin, who had no hesitation in ruling him out.

"Because it was head-related, they told me to rest and ruled me out," Hilder said last night. "I've never had it before, but they're sending me for a CAT scan, more as a precaution than anything else."

Dr McGeoch said the symptoms could be related to a viral infection or migraine, "but we're not really sure so we'll do some investigations this week".

Back-rower Cameron Ciraldo, who had played all 80 minutes for Central Newcastle in the NSW Cup game, was warming down with teammates when coach Brian Smith asked him to sit on the bench for first grade. Ciraldo came on in the second half and played 23 minutes.

"He [Smith] asked me if I was right to play, and I thought it was a trick question, but he was serious. It was good to get a chance to play because you always want to play first grade, no matter what," Ciraldo said. "The other game wasn't too fast and there were a lot of breaks, so I didn't feel too bad."

Halfback Scott Dureau is in extreme doubt for the game against the Roosters at Bluetongue Stadium on Sunday after hobbling from the field in the 57th minute yesterday with ankle and hip injuries.

He had been crunched in a Greg Eastwood tackle six minutes earlier.

Adam MacDougall's troublesome left knee was slightly swollen at training on Saturday. He could not run flat out so withdrew, and Keith Lulia started in his place. Smith believed MacDougall and Jarrod Mullen (calf) were strong chances to return against the Roosters.