The Highlanders have made some changes to their forward pack to face the South Africans.
Manu will begin the match in the reserves, with Elliot Dixon getting the start at No 8. The other candidate to start off the back of the scrum, TJ Ioane, pulled a calf at training earlier this week, and will be unavailable for a couple of weeks.
Manu was struggling with an ankle injury earlier this week but should be good enough to come off the bench.
Kane Hames returns to the front row after missing last week because of suspension, with Chris King moving across to the tighthead side. Thorn is back in the starting side, replacing Jarrad Hoeata.
Patrick Osborne returns to the left wing to replace the suspended Kurt Baker.
Highlanders coach Jamie Joseph was expecting nothing less than a tough contest from a wounded Bulls side, which has spent the last few days in Queenstown resting up.
Joseph said the Bulls had upset some good teams.
''Any team that is wounded is going to be a handful ... they are a very, very strong rugby team. They taught us a bit of a lesson at Loftus last year, but previous to that we have had a bit of success against the Bulls,'' Joseph said.
''But this is going to be a very tough team. There are obvious things that they are good at ... physically it is going to be a hell of a match. And our forwards need to get out there and match them.''
The Highlanders will know what is coming tomorrow night and even more so with the selection of lock Victor Matfield, the former Springbok captain with more than 100 test caps to his name.
Matfield, who turns 37 next month, will face off in the second row against 39-year-old Thorn, in what will be a battle of hard men.
Matfield had originally intended to come on tour just as a coaching consultant to Bulls coach Frans Ludeke.
But injuries in the side's loss to the Hurricanes last week has forced Matfield to get his boots out again.
His experience and ability around the field is a huge plus for a Bulls side which is going through a period of transition this year as players move on and youngsters are introduced.
He will be partnered in the second row by captain Flip van der Merwe.
Prop Werner Kruger will play his 100th game for the Bulls in Super rugby tomorrow night, after making his debut in 1998.
First five-eighth Jacques-Louis Potgeiter has shrugged off a blow to his leg picked up in the Hurricanes game and will be a key for the Bulls with his goalkicking.
Highlanders v Bulls
Forsyth Barr Stadium, tomorrow, 7.35pm
• Highlanders: Ben Smith (captain), Richard Buckman, Malakai Fekitoa, Shaun Treeby, Patrick Osborne, Lima Sopoaga, Aaron Smith, Elliot Dixon, Shane Christie, Gareth Evans, Joe Wheeler, Brad Thorn, Chris King, Liam Coltman, Kane Hames. Reserves: Ged Robinson, Craig Millar, Ma'afu Fia, Jarrad Hoeata, John Hardie, Fumiaki Tanaka, Trent Renata, Nasi Manu.
• Bulls: Jurgen Visser, Akona Ndungane, JJ Engelbrecht, Jan Serfontein, Bjorn Basson, Jacques-Louis Potgeiter, Francois Hougaard, Grant Hattingh, Jacques du Plessis, Jono Ross, Victor Matfield, Flip van der Merwe (captain), Werner Kruger, Callie Visagie, Dean Greyling. Reserves: Bongo Mbonambi, Marcel van der Merwe, Morne Mellett, Paul Willemse, Jacques Engelbrecht, Piet van Zyl, Handre Pollard, William Small-Smith.
