Northern Bulls scored three tries in six minutes to set up a 48-18 triumph over Southern Kings Saturday and rise to second place on the Super 15 standings.
The bonus-point South African derby win lifted the Bulls to 59 -- level with the inactive Australian ACT Brumbies on points, but ahead because they have one more victory this season in the southern hemisphere championship.
Waikato Chiefs top the table by two points after a 34-22 home win over fellow New Zealanders Wellington Hurricanes, but the title-holders have a tough finish to the league stage with visits to Canterbury Crusaders and Auckland Blues.
Bulls, three-time winners of the Super Rugby title and the only South African side to lift the trophy, complete their schedule by hosting the Coastal Sharks and visiting the Western Stormers in all-South African clashes.
Brumbies, coached by South Africa's 2007 Rugby World Cup-winning coach Jake White, have just one league fixture left, away to fellow Australians Western Force in August after the British and Irish Lions tour.
The table-toppers receive a bye into a home semi-final and, if victorious, a home final too. A travel-exhausted Sharks side played away in the quarter-finals and semi-finals last year and took a 37-6 final pounding from the Chiefs.
But while the Bulls celebrated a six-try-to-two victory at Loftus Versfeld, defeat condemned the Kings, from Indian Ocean city Port Elizabeth, to a two-leg play-off against the Golden Lions for a Super 15 place next season.
Kings, a second-tier domestic side, replaced the top-tier Lions this year after the Johannesburg outfit were the lowest South African finishers in the 2012 Super 15 competition.
The goal was to boost rugby union in the eastern Cape, where there is the largest concentration of black players in the country, but the Kings have managed just three wins in 14 outings.
After restricting the Bulls to a 10-6 lead approaching the half-hour mark, hooker Chiliboy Ralepelle, centre Jan Serfontein and scrum-half Francois Hougaard went over for tries that fly-half Morne Steyn converted.
A Wimpie van der Walt try trimmed the Bulls' half-time advantage slightly to 31-13 and another touchdown from the flanker 13 minutes after the break trimmed the lead further.
But the rest of the match belonged to the home side with loose forwards Jacques Potgieter and Deon Stegmann claiming a try each and Steyn adding two conversions for an 16-point haul.
The planned 'rest' for Steyn did not materialise as he came off the bench early in the first half to replace fly-half Louis Fouche, who scored and converted the first try.
Springbok Steyn slotted five conversions and two penalties from eight shots at goal while rival playmaker Demetri Catrakilis also missed only once while landing two penalties and a conversion.