Stuff sports reporter Ben Strang and referee Nick Briant explain the rules about offside around the tackle and ruck.

OPINION: Defensive lines, and particularly the All Blacks, launch at attacking teams with such pace it appears they are always flouting the offside rules.

Each week referees come in for a verbal hiding for not enforcing the offside laws, allowing defensive teams to creep up and shut down any space for the attacking team to run.

Most of the time the referee is right in not pulling a team up for being offside and, in fact, some of the offside calls referees do make are incorrect.

CAMERON SPENCER/GETTY IMAGES All Blacks captain Richie McCaw and coach Steve Hansen reflect after their humbling defeat in Sydney.

The reason for the confusion is the difference between a tackle and a ruck.

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When a tackle is made there is no offside line. A ruck is only formed when a player from each team comes into contact over the ball, and only then does an offside line run through the hindmost foot of the hindmost player in the ruck.

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Often when the All Blacks are defending they don't even attempt to form a ruck, hence no offside line.

It appears a dedicated tactic by the All Blacks to help their defensive structure, allowing them to shut down the opposition faster.

In truth the All Blacks could take it much further, standing in the attacking side's backline as long as they are more than one metre from the tackle area.

They don't for a number of reasons. The All Blacks probably back their defensive structures as they are, but it would also cause utter chaos if they did choose to stand shoulder to shoulder with their opposition.

The other reason is whether the referee will make the right decision, which can often come back to bite them. For instance, Handre Pollard's 56th minute penalty against the All Blacks was for offside, but the New Zealand defenders never committed players to form a ruck, meaning it was the wrong call.

Against South Africa, New Zealand made 94 tackles. Of those 94 tackles, only 41 turned into rucks or mauls, meaning 56.4 per cent of the time there was no offside line.

It was the same against Australia. The All Blacks made 121 tackles against the Wallabies, forming only 54 rucks or mauls, meaning 55.4 per cent of the time there was no offside line.

Australia and South Africa also use the tactic, but place far more emphasis on sending players into the tackle to try and win the ball.

South Africa formed a ruck on 67 per cent of their 85 tackles against the All Blacks, while Australia sent players into the ruck on 63.5 per cent of their 85 tackles as David Pocock and Michael Hooper found plenty of success.

Another interesting thing to note is the number of times the All Blacks actually commit players to the ruck on defence.

More often than not they leave it to the tacklers to get to their feet and contest for the ball, with players only coming in to support when they are confident of winning a turnover.

Of the 41 rucks against South Africa, New Zealand sent extra men in only 21 times. Five of those occasions New Zealand forced a turnover or penalty for a 23.8 per cent success rate.

When you watch the All Blacks attempt to defend the Bledisloe Cup on Saturday, watch how often they actually form a ruck.

You'll be surprised. Maybe Richie McCaw doesn't cheat as much as you think.