Co-captain Aidan Guerra admitted sagging confidence was becoming an issue for Newcastle after they slumped to their worst defeat of the NRL season.
Having started the season promisingly with back-to-back wins, the Knights have now lost four on the trot after conceding nine tries in a sorry 48-10 defeat to Cronulla on Sunday.
The frailty of their defence had Guerra questioning whether it was a mental problem.
Asked if confidence was an issue, Guerra said: "It's starting to become one. It wasn't to start with.
"As a side, we just need to build the ability to stop tries when things aren't perfect because in this game, a lot of situations aren't perfect, especially when you're defending your line.
"We've just got to band together and start coming up with some try-savers...we came up with a few at the start of the season."
Knights coach Nathan Brown accused his team of conserving themselves for attack.
"We defend waiting to get the ball back and save a bit of energy for offence, where we need to front-load more energy in defence," he said.
"It's a great lesson for a lot of our younger players that our defence is important and you need to frontload all your juice into that."
Brown also said there was no use laying the boot in a team that is unlikely to change for next week's clash against another side struggling in Parramatta.
With Brock Lamb, Mitchell Pearce, Jacob Saifiti and Tautau Moga on the long-term injury list, Brown has few options available to tinker with his line-up.
The club will also need to monitor centre Nathan Ross after he aggravated a groin injury.
"It's no good me publicly getting stuck into all the guys. The group that played today plus another 2-3 players are the same blokes that need to perform a hell of a lot better next week," Brown said.