Willemse came off the replacements’ bench in the victory against the Eastern Province Kings in Port Elizabeth last week, and he gets his first opportunity in the starting lineup at openside flank, with Kobus van Dyk shifting across to the blindside and Jurie van Vuuren starting on the bench.
The only other changes come in the backline as Robert du Preez starts at flyhalf and Johnny Kotze comes in at outside centre, with Huw Jones moving across to inside centre.
There are two new backline players on the replacements bench as well, with scrumhalf Dewaldt Duvenage back in the mix for the first time since returning from France, and utility back EW Viljoen called up from Western Province U21.
The versatile Duvenage will cover both scrumhalf and flyhalf, having played in both positions for the Stormers in the past.
Western Province coach John Dobson said that the team is excited to play in front of their faithful fans at Newlands in what should be a hard-fought coastal derby.
Western Province: 15 Cheslin Kolbe, 14 Werner Kok, 13 Johnny Kotze, 12 Huw Jones, 11 Leolin Zas, 10 Robert du Preez, 9 Jano Vermaak, 8 Sikhumbuzo Notshe, 7 Kobus van Dyk, 6 Stefan Willemse, 5 Chris van Zyl (capt), 4 JD Schickerling, 3 Wilco Louw, 2 Scarra Ntubeni, 1 JC Janse van Rensburg.
Replacements: 16 Neil Rautenbach, 17 Alistair Vermaak, 18 JP Smith, 19 Jan de Klerk, 20 Jurie van Vuuren, 21 Dewaldt Duvenage, 22 EW Viljoen.