All Blacks: Steve Hansen identifies speed trap as biggest 2019 Rugby World Cup danger

The common denominator of the All Blacks' struggles over the last few years – the defeats to Ireland, the British and Irish Lions, and South Africa - is their inability to cope with a defensive line speed which shuts down their time and space and which they are expecting more of at the World Cup.

Head coach Steve Hansen brought it up unprompted last night during the announcement of the 39-player Rugby Championship squad in Auckland, which featured another surprise in the form of Liam Squire's decision to make himself unavailable.

The suffocating and successful pressure other nations have put on the All Blacks' backline - and in particular No10 Beauden Barrett - is obvious and it's a blueprint every other team will attempt to replicate in Japan.

That the All Blacks coaches are aware of it and are making it a clear priority is obviously a positive. The key will be in successfully putting their training ground strategies on to the pitch, especially against Australia in the Bledisloe Cup and in Japan during the World Cup – the All Blacks' two priorities this year (starting with the lowest first).

Opposition teams like Ireland have been successful when putting Beauden Barrett under pressure with a quick defensive line speed. Photo / Getty

Should the All Black pack gain at least parity in the big tests, which it should, then the key could be in the kicking game of first-fives Barrett and Richie Mo'unga, and both showed a variety last weekend during the thrilling Super Rugby semifinal in Christchurch that will please Hansen and his assistants.

Barrett has struggled in Christchurch over the last three years due to the line speed created by the Crusaders but such was his influence and that of his halfback TJ Perenara that the Hurricanes nearly came back in the second half to cause a big upset and that was largely due to the pair kicking in behind the Crusaders' rush defence.

Mo'unga was similarly good and will get another chance to impress in Saturday's grand final against the Jaguares, but Barrett can take a lot of positives from that performance. It was one that underlined his quality once and for all - even, possibly, to Mo'unga's most fervent supporters.

The other notable revelation from the announcement was Squire's decision. It appears that the Highlanders flanker has left the door open for a place at the World Cup, but it's no certainty he'll be selected, especially if new cap Luke Jacobson, a Chiefs loose forward who has impressed hugely this season, takes his opportunities.

In Jacobson's favour is his versatility, which Hansen mentioned, and the fact he is just starting his career in New Zealand whereas Squire is heading offshore at the end of the year.

The only other recent example of a player denying the selectors the chance to pick him in a black jersey is Brad Thorn, a lock who became an All Black great for his toughness and exploits during, among other tests, the 2011 World Cup final, and who, like Squire is perhaps more sensitive than many realise.

Thorn went from league in Australia to the Canterbury NPC team in 2001 and was picked for the All Blacks' end of year tour but pulled out due to his uncertainty at whether he was fully committed to rugby union. He ended up playing 59 tests for the All Blacks from 2003-11.

Those who know Squire say he takes things to heart more than he probably should, although it's not known what is behind either his personal issues which prevented his selection for the Highlanders this season or his latest refusal.