The 20 year old has played off the bench twice in his debut season, but now gets a chance to stake a more permanent claim to the number 12 jersey.
Serfontein swops places with Francois Venter, who will revert to the bench, as Vodacom Bulls coach Frans Ludeke made two more changes in the backline.Jürgen Visser will start at left wing in place of Bjorn Basson, who has an ankle injury, while Mornè Steyn is back as pivot after Louis Fouchè got a start last week.
Up front, Grant Hattingh (broken thumb) is replaced by Juandrè Kruger, while Wilhelm Steenkamp, who flew to Australia earlier in the week as a replacement, will play off the bench. Arno Botha, who was rested against the Reds last week, will be used as impact player ahead of Jacques Potgieter.
Deon Stegmann recovered from his hamstring strain to the leave the loose trio intact.
The team to play the Brumbies:
Zane Kirchner, Lionel Mapoe, JJ Engelbrecht, Jan Serfontein, Jürgen Visser, Mornè Steyn, Jano Vermaak, Pierre Spies (c), Dewald Potgieter, Deon Stegmann, Juandrè Kruger, Paul Willemse, Werner Kruger, Chiliboy Ralepelle, Morne Mellett. Replacements: Willie Wepener, Frik Kirsten, Wilhelm Steenkamp, Arno Botha, Ruan Snyman, Louis Fouche, Francois Venter.