The big lock will start for the Highlanders in Taupo this afternoon against the Chiefs, in the first pre-season match of the season.
Highlanders coach Jamie Joseph said Thorn, who will turn 38 tomorrow, had been playing Japanese club rugby and needed to make the transition back to Super rugby.
''The best way to do that is get the boots on and get back on the field,'' Joseph said.
''With the All Blacks coming back and the level that they train at, and they way they train, is really encouraging for a lot of our younger guys.''
Ma'a Nonu trained once with the Highlanders this week and then went back to Wellington to complete his shift south and would join the camp fulltime on Monday.
He is not available to play the Chiefs, while All Black prop Tony Woodcock is also being rested.
But all other players in the squad will travel north in a match where the result will mean little to Joseph.
''I don't really take much notice of the results in these games but I will be disappointed if we don't come away with some positives from the game.
''We need to measure some of the systems we have put in place over the past couple of weeks and see how they go. Before Christmas it was more about strength and conditioning and now we are talking about starting to play the game in both attack and defence.''
Thorn will lock the scrum with another new Highlander, Joe Wheeler, while Jarrad Hoeata will start at blindside flanker, an indication of where he may play much of his rugby this year.
It is also a chance for No 8 Elliot Dixon to stake an early claim after a limited two years with the Highlanders.
Lima Sopoaga will start in the number 10 jersey, as Colin Slade is not ready to play. It will be touch-and-go whether Slade is ready for the start of the season.
Ben Smith will stay at full-back, after there were suggestions he might move into centre after Tamati Ellison went down with a damaged shoulder. Phil Burleigh will team up with Shaun Treeby in the midfield.
Liam Coltman will get the start at hooker and will be keen to make an impression, with captain Andrew Hore sidelined for the opening game of the competition.
Otago lock Tom Franklin has joined the squad as injury cover for both Jake Paringatai (broken hand) and Nasi Manu (hamstring). Franklin should get a run off the bench.
Hosea Gear will captain the side from the left wing in Hore's absence.
Joseph conceded the weather was hardly ideal for rugby. Taupo is forecast to reach 26degC today. The sides were scheduled to play 40-minute halves but this may change.
These pre-season games are a chance to get out on the paddock and see how patterns work. But as a guide to the season they are about as accurate as a Novopay payroll. The Highlanders lost all three pre-season games last year and then won their first four games in the competition. So it is more about what is happening on the paddock than on the scoreboard.
The Chiefs will not field the bulk of their All Blacks. This is the first of three meetings between the two teams in the next two months. The sides will kick off the Super 15 at Forsyth Barr Stadium on February 22 and meet again in Hamilton exactly one month later.
Highlanders v Chiefs
Taupo, today, 3pm
Highlanders: Ben Smith, Buxton Popoali'i, Phil Burleigh, Shaun Treeby, Hosea Gear (captain), Lima Sopoaga, Frae Wilson, Elliot Dixon, Tim Boys, Jarrad Hoeata, Joe Wheeler, Brad Thorn, Ma'afu Fia, Liam Coltman, Jamie Mackintosh.
Reserves: Jason Emery, Tony Ensor, Kade Poki, Hayden Parker, Trent Renata, Aaron Smith, Fumiaki Tanaka, Josh Bekhuis, Hugh Blake, Tom Franklin, Paul Grant, Brayden Mitchell, Bronson Murray, Sam Prattley.
Chiefs: Tim Nanai-Williams, Lelia Masaga, Charlie Ngatai, Andrew Horrell, Maritino Nemani, Gareth Anscombe, Augustine Pulu, Fritz Lee, Tanerau Latimer, Matt vant Leven, Michael Fitzgerald, Craig Clarke (captain), Ben Afeaki, Hika Elliot, Toby Smith.
Reserves: Rhys Marshall, Michael Kainga, Ben Tameifuna, Romana Graham, Ross Filipo, Brendon Leonard, Bundee Aki, Pauliasi Manu, Patrick Osborne, Solomoana Sakalia.
