The inclusion of Jantjies and Pretorius are the only changes from the team that started the win against Scarlets in Llanelli to clinch the South African Shield in the final game of the regular season.
The DHL Stormers will face the Scottish team at 19h00 on Saturday, with gates at DHL Stadium opening at 17h00.
Jantjies starts at scrumhalf, while Pretorius is at inside centre in place of Damian Willemse, who has been ruled out due to an arm injury. The only other changes to the matchday squad see lock Adre Smith and Junior Springbok utility back Sacha Mngomezulu, who is in line to make his Vodacom URC debut, included among the replacements.
DHL Stormers head coach John Dobson said that his team want to make the most of the opportunity to play a quarterfinal in front of their faithful supporters.
"A lot of hard work has gone into securing this home quarterfinal, so we are determined to rise to the occasion," said Dobson.
"It has been a good week of preparation and everyone is excited about what should be a memorable day. We want to raise the intensity and make sure that we are at our best for the full 80 minutes, playing the kind of rugby that has got us into this position."
Dobson said that while Damiam Willemse had been given as much time as possible to prove his fitness, it was decided not to risk him with Pretorius ready to step in.
"We gave Damian as much time as we could to make it for this match, but in the end it was not worth the risk, especially as we have a quality player in Rikus to start at 12. It also gives the talented Sacha Mngomezulu an opportunity to show what he can do when he comes on," the coach added.
DHL Stormers: 15 Warrick Gelant, 14 Seabelo Senatla, 13 Ruhan Nel, 12 Rikus Pretorius, 11 Leolin Zas, 10 Manie Libbok, 9 Herschel Jantjies, 8 Evan Roos, 7 Hacjivah Dayimani, 6 Deon Fourie, 5 Marvin Orie, 4 Salmaan Moerat, 3 Frans Malherbe, 2 JJ Kotze, 1 Steven Kitshoff (captain). Replacements: 16 Andre-Hugo Venter, 17 Brok Harris, 18 Neethling Fouche, 19 Adre Smith, 20 Ernst van Rhyn, 21 Nama Xaba, 22 Godlen Masimla, 23 Sacha Mngomezulu.