Brisbane coach Anthony Griffin says his players need to be careful not to "fall in love with themselves" after 160 minutes of second half defence without conceding a try this season.

With their attack yet to click, Brisbane have strung together three successive wins on the back of some courageous and inspiring defence.

Their tryline has not been breached in the second half of their four games so far.

It's a statistic Griffin knows can't last much longer and one which he warns can pose a mental threat if his players start believing they have got it all together.

Griffin has put a lot of time and effort into getting his defensive structure and patterns right but he knows much of it comes from the players' attitude which has to be spot on against Newcastle next Monday night.

"We've been good (defensively) but it's really important we don't fall in love with ourselves and start thinking we're just going to go and it's going to happen," he said after naming an extended 20-man squad on Tuesday.

"It's a really hard thing to get right. It's the hardest part of the game to get right and we've done a great job to get ourselves to this point.

"When we get back to work (training) on Wednesday we've got to get down and get dirty again and get ready for Newcastle."

Brisbane went from the worst defensive side in the NRL at the start of last season to its best in the middle rounds before falling back into some bad habits as they missed the NRL finals under Ivan Henjak for the first time in 18 seasons.

"At times last year it (defence) was really good. The middle part of last year we went through eight or nine games where we were the best defensive team in the competition," he said.

"The issue was the first six and the last six games we were probably the worst.

"We've been building a foundation there from last year and we worked hard on it in the off-season.

"At the moment, they're playing for each other and that's the main thing with defence no matter what system you've got, if you haven't got an attitude that you want to play for each other, then it's going to fall down."

Fullback Josh Hoffman (corked shin) and utility Ben Hunt (knee) will miss the clash with Griffin likely to use Alex Glenn as hooker Andrew McCullough's back-up.

"Josh Hoffman and Ben are not going to make it so we've got to make a decision on how we handle the utility position," he said.

"We've got a bit of maintenance with a couple of the tight forwards, so we're going with a squad of 20 for now until Sunday when we finalise the 17."

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