Thorn was rested while New Zealand beat Scotland 32-6 at Murrayfield last weekend. It was a selectorial decision that did not exactly sit comfortably Thorn, 33, a consummate footballing professional.
Thorn has hardly been over-extended since the season's third test against the Wallabies in Brisbane in mid-September.
Once the All Blacks had retained the Bledisloe Cup and Tri-Nations title at Suncorp Stadium, he was confined to gym routines and aerobic conditioning in Christchurch until he sought, and was granted, permission to make his debut for Tasman in their Air NZ Cup quarterfinal against his old province Canterbury.
Thorn plugged away for an hour, his only game time outside a trial match in Auckland before the All Blacks left on October 27 for their historic offshore Bledisloe test in Hong Kong.
Such a light preparation might concern a lesser athlete, but not for Thorn as he muscled through the heat and humidity, displaying a work ethic that has characterised a career containing 214 games for the Brisbane Broncos, eight tests of the Kangaroos, 14 State of Origins for Queensland and a combined 88 appearances for the Crusaders and Canterbury.
Hard graft has been ingrained in his psyche since he signed on at the Broncos as a teenager.
When he missed the 22-man squad to play Scotland, it took a tetchy Thorn "about half a day" to accept the rationale in grooming Anthony Boric as the squad's third choice lock.
"It's just 'cos I like to play," said Thorn of his omission.
"From my experience I notice if I've had a break, it makes it a bit harder the next time we play.
Thorn's opinion is based on his long association in the National Rugby League, a competition that gives the concept of player rotation little credence.
"My history is playing 24-26 rounds (of NRL) plus (State of) Origin, plus Australia .... it's just what I'm conditioned to, it's what I feel comfortable with.
"In saying that, there's 35 guys on this tour and some of them haven't got to play at all yet."
Thorn is fired up for Sunday's test against the Irish at Croke Park, the first time the teams have met at the home of Gaelic football.
For Thorn, his 22nd test also denotes a milestone in his remarkable career, a first cap in the northern hemisphere.
He might have joined Richie McCaw and Aaron Mauger in making his test debut at Lansdowne Road in 2001 but famously declined to tour because he was not convinced he could commit to rugby after one Super 12 and NPC campaign in Christchurch.
Thorn eventually settled and belatedly made his All Blacks debut against Wales in 2003 and played through to that year's World Cup.
After the All Blacks' semifinal exit he returned to the Broncos for three seasons and thought he would wind up in Britain playing Super League.
However, Robbie Deans sounded him out for another Crusade, he agreed and in no time Thorn's second coming as an All Black became inevitable.
He has played nine of the 12 tests this season and is relishing the opportunity to take on the Irish for a second time this year.
Thorn's comeback to test rugby in June coincided with the All Blacks' season-opening 21-11 win in Wellington and he was expecting another difficult encounter combating the established Irish pairing of Paul O'Connell and Donncha O'Callaghan.
"They're very solid. O'Connell is a leader -- all those Munster guys are battle hardened -- they've won big games.
"It's a daunting task, we actually really rate these guys."
Fellow lock Ali Williams said Thorn continued to be an inspiration.
"The way he trains, the way that he still enjoys himself day in and day out around a team environment where he's been and done everything since 16 is amazing," he said.
"On the field he just gives everything. Maybe he might not feel 100 per cent on one game but he'll give everything of what he's got. If I could have half the career he's had I'd be pretty happy."
