Gear will still be available for Worcester's clash with Bourgoin in France later the same week.
South Africa's Bryan Habana, together with All Blacks Joe Rokocoko and Wales star Shane Williams are other wingers in the squad.
Barbarians committee member and former England prop Mike Burton said: "Assembling such a star-studded squad from several countries would not have been possible without the approval and co-operation of national unions and individual provinces and clubs.
"We are grateful for the support we continue to receive. Many people in many different capacities recognise the role of the Barbarians in such high-profile fixtures, and their encouragement is a huge boost to all of us who are involved. It promises to be a great occasion in every respect."
Backs: P Montgomery, B Habana, J Rokocoko, S Williams, R Gear, J de Villiers, O Smith, F Trinh-Duc, G Gregan, F du Preez.
Forwards: P Collazo, G Steenkamp, C Hayman, J Smit, M Regan, B Botha, S Borthwick, C Jack, N Koster, S Burger, J Collins, R McCaw.