As far as back-up plans go, St George Illawarra coach Nathan Brown is fast running out of letters in the alphabet.

Brown may be forced to make yet another change to his halves combination, with five-eighth and skipper Ben Hornby injuring his quadricep and putting himself in doubt for tonight's NRL match against North Queensland at WIN Stadium.

Hornby suffered the injury, which is expected to sideline him for only one week at most, at training on Thursday night. The Dragons will give him right up to the whistle to recover.

If he is ruled out, young gun Richie Williams will partner Mathew Head at the scrumbase, the game against the Cowboys Head's first following a long rehabilitation from knee surgery.

It must seem like light years away when Brown was planning his attack around a Mark Gasnier-Ben Hornby scrumbase pairing, the Williams-Head combination his fourth combination of the year before the third round of the competition.

"We still haven't got our game - as far as our attack goes - to where we want to get it, which makes it a bit unfortunate that Benny got hurt," Brown said yesterday. "We didn't want to lose Benny but it's a positive that we can bring in Heady.

"No Benny, no Heady, no Gaz, no Simon [Woolford] - that would have been very disappointing, but to have Heady there it gives us some stability.

"Heady's greatest attribute is that he makes people around him look good, and there's not bucketloads of halfbacks around these days that have that ability.

"He's obviously not as athletic [as some other halfbacks], he's not real big, but he has an ability to put the ball where the ball needs to go to make other people look good.

"He is the best player in the club at building pressure - that's an area where we've been letting ourselves down lately."

It was particularly evident against Newcastle last week when the Dragons were unable to hold on to a four point-lead against the fast-finishing Knights.

Holding a four-point lead with 12 minutes remaining is a position the Dragons would love to find themselves in tonight, but there are serious question marks over whether Brown's inexperienced batch will be able to withstand the early onslaught from the Cowboys.

Led by brilliant halfback Johnathan Thurston and elusive fullback Matthew Bowen, North Queensland have joined Melbourne as the early favourites for the premiership following wins over premiers Brisbane and the Sydney Roosters.

The only hiccup for the Cowboys heading into the game against the Dragons has been the loss of veteran Jason Smith with an ankle injury, but with former Queensland Origin winger Ty Williams the only other injury concern, coach Graham Murray has plenty of talent from which to choose.

"We had to make changes when we won [in round one]. Unfortunately, we had to leave Mark Henry out," Murray said. "Every week we are trying to put out our best possible 17 or 18 to travel."

As to who will fill in for Smith at pivot, Murray said he would wait until tomorrow to make a final decision.

"Justin Smith's probably the obvious one there, and [Aaron] Payney's done a job at seven before so that may bring [David] Faiumu in, so there are a few options."

The Dragons head into the match having won their past three games against the Cowboys by a margin of 20 points or more, but this Saints side bears little resemblance to last year's, with only five survivors from the side that beat North Queensland 34-14 in round 16 last year.

Meanwhile, Newcastle captain Andrew Johns has been given the all clear from doctors to make his return from concussion against Canberra on Monday night.

The champion halfback underwent a cognisance test yesterday with the club's medical staff giving the 32-year-old the green light to play at Canberra Stadium.

Johns was knocked out in the fourth minute of the Knights' opening-round win over the Bulldogs after being on the receiving end of a Sonny Bill Williams high shot.

He was cleared of any facial fractures, but missed last week's game against St George Illawarra because of severe concussion.

Johns scored 30 points, including two tries, the last time he was in Canberra in a record 70-32 win for the Knights in round two last year.

AAP