The Blue Bulls were made to sweat by the tailenders Valke before emerging victorious 22-20 in an Absa Currie Cup game at Loftus.
Coach Frans Ludeke had fielded a second-string team that did not disappoint on Friday as they ended the domestic campaign on a high note.
He had rested seven of his regular Springbok players, including captain Victor Matfield, after they had clearly booked a home semifinal berth a week before the weekend's clash.
The Bulls host defending champions Cheetahs in the first semifinal in Pretoria on Saturday.
Meanwhile, the Sharks ended this year's campaign on top of the Absa Currie Cup log after trouncing Griquas 66-12 in Durban.
They play the Lions in the other semifinal on the same day (Saturday) in KwaZulu-Natal.
Other results: Western Province 14, Lions 6; Cheetahs 50, Kavaliers 40.