Northern Bulls lost first place in the Super 15 table after a final-round 30-13 hammering at Western Stormers Saturday.
The Cape Town side played inspirational rugby at Newlands and left supporters wondering how they could finish only seventh and miss the play-off series.
Bulls had no answer to the brilliant attacking and defending of their long-time foes, and slipped to second on the final standings.
Waikato Chiefs of New Zealand collected 66 points, Bulls 63 and ACT Brumbies of Australia 60 to occupy the top three places as national conference winners.
Brumbies host Central Cheetahs of South Africa in the play-offs and Canterbury Crusaders of New Zealand meet Queensland Reds of Australia.
"It was nice to give something back to our supporters after an overall disappointing season," said Stormers skipper and centre Jean de Villiers.
"Everyone played well tonight. We are a quality team and there was also so much passion in our performance."
Bulls skipper and No.8 Dewald Potgieter wore a plaster below his left eye as testimony to the fierce forward exchanges.
"We are naturally disappointed as top place after the league phase has been our aim since the start of the season.
"At least we have a week off to allow players to recover from injuries and prepare for the semi-finals. I know all South Africans will be behind us."
A bonus-point New Zealand derby victory for Chiefs over Auckland Blues meant the Bulls needed to make it 10 wins in a row to remain on top.
But they were on the back foot from the kick-off and lock Eben Etzebeth powered over for a 10th-minute try and a lead the Stormers never lost.
Bulls' happiest moment was when full-back Zane Kirchner dotted down and star fly-half Morne Steyn converted to leave the Bulls 14-10 adrift.
However, recalled Stormers fly-half Gary van Aswegen then kicked three penalties to one by Steyn and the Cape outfit turned over 23-13 ahead.
De Villiers was sin binned just before half-time for a high, late tackle only to make amends with a match-clinching try on 56 minutes.
Van Aswegen converted to close the scoring and his 15-point haul plus an inventive general display earned him a standing ovation when he was benched.
Fittingly, Stormers left-wing Bryan Habana had the final say as he tapped a penalty into touch to end a typically bruising South African derby.
A 2007 Rugby World Cup winner and former Bull, Habana, 29, is leaving Cape Town for French Top 14 outfit Toulon.
He scored the Stormers' other first-half try, cutting inside to take a De Villiers pass and dot down with a trademark spectacular dive.
Steyn, the leading Super 15 points scorer this season with 230, had to settle for eight in Cape Town as he also kicked two penalties.
But his mid-second half departure along with scrum-half and fellow Springbok Jano Vermaak indicated that the Bulls' bosses knew this was not their day.
After a bye next weekend, they face the higher ranked of the play-off winners -- probably the Brumbies -- in a Pretoria semi-final.
Title-holders Chiefs also get a brief break before a potential semi-final showdown with compatriots and seven-time champions the Crusaders.