The defensive system dubbed 'The Blue Wall' that's confounding Super Rugby has a northern hemisphere coach masterminding it

NSW Waratahs have labelled their much improved defence the Blue Wall and its certainly proving harder to breach than in recent Super Rugby seasons.

After conceding 19 tries in their first five games in 2017 and and 17 last year, the 'Tahs have only allowed 13 five-pointers this season

Asked what the difference was this year, backrower Ned Hanigan said new defence coach Steve Tandy had brought greater clarity in that area.

'It's not that different, it's just blokes staying more connected with one another and you're just trusting the fellows inside and outside you have got your back," Hanigan said.

'It sounds simple but really practising it and making sure you don't have those rogue guys.

"That Blue Wall is what we refer to it as and you just keep turning up."

Welshman Tandy praised the players for buying in and for how they were applying the system.

"The boys are getting more trust and connection in how they go about their busi ness and around working together and making good choices around it and its just something that seems to be growing," Tandy said.

NSW haven't conceded more than three tries in a game this season and last Saturday kept the free-scoring Crusaders down to two, one of which was scored in the dying seconds.

"Coming up against the Crusaders, we knew that was going to be a real barometer around where we were defensively," Tandy said.

"They do a lot of passes, they run a lot of variety around their shape, they've got good ball carriers, so it; was really nice to stand up to that sort of test.

"I thought our discipline was outstanding, and we trusted our system.

'We only gave three penalties away in a game coming up against the Crusaders is pretty special."

Former NRL star Karmichael Hunt has added some starch to the midfield this year and was inspirational off the bench last Saturday with a huge hit late in the game.

"Karmichael comes off the bench and it's just carnage wherever he goes, it definitely lifts the team," Hanigan said.

The Waratahs head the Australian conference by one point ahead of Melbourne Rebels with just four points separating the four local teams.

NSW host the conference's bottom placed side the Sunwolves in Newcastle next Friday.

Lock Jed Holloway is in doubt for the game with a rib injury.