The Sharks upset the Stormers' Super 14 party with a hard-fought 20-14 victory which ensures the Bulls will finish next weekend at the top of the Super 14 table.
Sharks coach John Plumtree had said before the Durban clash that his team would not let up despite having nothing to play for except pride - and he was right.
The Sharks played their match of the season with an intensity not seen before, keeping the Stormers on the back foot.
In contrast, the Stormers turned in a flat, uninspiring performance. Their first-half display was easily their worst of the season and they could have trailed by more than 14 points at the break.
The Sharks had a strong wind at their backs in the first half, pinning their opponents back in their own 22 from the kick-off.
The first score came when Sharks right wing Odwa Ndungane rounded the Stormers defence in the seventh minute - Pienaar's conversion made it 7-0 after as many minutes.
And in the 38th minute Pienaar himself crossed, after Sireli Naqelevuki failed to execute a regulation dot down from a nothing kick ahead from Ruan Pienaar. Instead of touching the ball down, Naqelevuki knocked it backwards, and Pienaar was through to score.
The Stormers gave themselves hope five minutes into the second half, with Peter Grant rounding off a well-worked move by scoring under the posts, then converting.
However, the same player then failed to score with a long-range penalty, while Pienaar did the same for the Sharks.
Yet Pienaar had his shooting boots on in the closing stages, giving his team much-needed breathing space with a penalty in the 66th minute.
And the game looked beyond the visitors going into the final five minutes after Pienaar again held his nerve to kick a penalty.
Ricky Januarie crossed for the Stormers in the final minute. Grant converted to give them a losing bonus point.
But if they lose next week they could miss out on hosting a Super 14 semi-final - and maybe even the semi-finals altogether.