The Stormers dented the Western Force's Super 15 finals prospects with a 24-8 victory in Cape Town on Saturday.
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The South African side were bottom of their conference before kick-off with just three wins in 11 matches but stunned their Perth-based opponents, second in the Australian group.
Even the loss of captain Schalk Burger through injury before kick-off could not halt the hosts, who had an early try by Nic Groom ruled out after the television official ruled that he had failed to release the ball after being tackled in the build-up.
Peter Grant's penalty did put the Stormers ahead before Juan de Jongh took full advantage of Cheslin Kolbe's inviting pass to touch down.
Sias Ebersohn reduced the deficit with a penalty only for the visitors to be reduced to 14 when Adam Coleman was sin-binned for illegally collapsing a maul just before half-time.
It was a costly foul as, while he was sidelined, the Stormers added 14 points with a penalty try awarded after Force collapsed a scrum close to their try-line and Grant's conversion have them a 17-3 half-time lead.
Ruan Botha charged over in the 46th minute for his first try for the club to extend the lead but the loss of Kolbe and Jaco Taute to yellow cards in quick succession slowed their progress and the Force's Matt Hodgson added a consolation try in the 70th minute.