The Newcastle Knights have conceded a total of 342 points in 2018 – the worst defensive record in the Telstra Premiership – with 146 coming in the past four matches.

The only other club over 300 is the Gold Coast Titans.

Following a 48-10 loss to the Cronulla Sharks described by coach Nathan Brown as the team's worst effort of the year, Knights captain Aidan Guerra said Newcastle had to rediscover some desperation in defence.

"As a side we just need to build the ability to stop tries when things aren't perfect," the forward said.

"In this game, a lot of situations aren't perfect, especially when you are defending your line, so we just have to band together and start coming up with some try-savers.

"In round one against Manly we had three or four, and against the Broncos we had another handful and that's the difference – today we had one.

"Every time they had an opportunity to score they did, and for a team who spoke about our defence at the start of the year, and said we need to improve, unfortunately it's not good enough."

Match highlights: Knights v Sharks - Round 12, 2018

Brown said his players were putting too much focus on attack.

"At the moment 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," Brown said.

"A classic example is we had a fair number of sets on the (Sharks') goal line in the first half in a 15-minute window, for three or four sets where we got penalties.

"They held us out, and then on the other foot, we defend the first set well, give away a tackle-five penalty and they score an easy try.

"That's the difference between the two footy clubs."

Brown said his team still needed to work on transferring the commitment shown at training into matches.

"I don't think these guys are doing a lot wrong. It's just when we get into these tough situations our confidence goes," Brown said.

"The reality is the guys at training have been training hard; their discipline is good, their talk is good – some of it is just not going to the field at the moment."