The Hurricanes and Highlanders will meet this weekend in a repeat of last year's Super Rugby final, though the primary focus of the 14th round will be the contest for playoffs places in South Africa.
With four rounds of the regular season remaining, the Bulls and Lions sit atop the two African conferences but their positions, and the playoffs places that go with them, are under threat from the Stormers and Sharks.
The Pretoria-based Bulls and Cape Town-based Stormers are level on 32 points in the Africa 1 conference but the Bulls have a superior win-loss record. The Johannesburg-based Lions, with 37 points, lead the Durban-based Sharks by two points in the Africa 2 conference.
The two conference leaders and the next best-placed team at the end of the regular season will advance to the eight-team playoffs, along with five teams from the conferences based in New Zealand and Australia.
The Bulls and Lions meet Saturday in Pretoria, while the Sharks have a bye.
The Stormers host the Bloemfontein-based Cheetahs and need to win to keep pressure on the Bulls and to end a dangerous late-season form slump. Losses to the Bulls and New South Wales Waratahs and a draw with Japan's Sunwolves in their last three matches have dropped the Stormers out of first place in South Africa for the first time.
Stormers assistant coach Russell Winter said the standings "changed drastically in the last two weeks."
"It's always been closely contested at the top there," he said. "There's never been a big gap in the points. One week changed the whole lot for us.
"But we realize that we have to go week to week and try to make sure that we are in a good position come the end of the tournament."
Springboks flanker Shalk Burger is likely to miss Saturday's match through injury but flyhalf Robert du Preez, Jaco Taute, Wilco Louw and Jean Kleyn are expected to return.
The Bulls vs. Lions encounter will be in the hands of South Africa's top referee, Craig Joubert, who will control his 100th Super Rugby match dating back to 2005.
"South African derbies have always been special to me and I'm thrilled to run out for the 100th time in Super Rugby," he said.
The Lions will be without flyhalf Elton Jantjies, who is sidelined for up to four weeks after surgery on a broken finger.
The Bulls will be defending the only unbeaten home record in Super Rugby this season when they start at at Loftus Versfeld.
"We made a decision at the beginning of the season, if we play at Loftus then we need to be up for it," coach Nollis Marais said. "We are playing possibly the best attacking side in South Africa and it is good for us to measure ourselves against them."
The second clash of the season between the Hurricanes and Highlanders, teams separated by a single point when they met in round two, will also be influential in the New Zealand conference.
The Highlanders won the first meeting 17-16 and have recently recovered the form that carried them to their first Super Rugby title last year, beating the Chiefs and Crusaders in their last two matches.
The Chiefs lead the New Zealand conference with 42 points, one clear of the Crusaders and five ahead of the Highlanders and six ahead of the Hurricanes. All four teams are in line for playoffs places but Friday's match and others in coming weeks between the Chiefs and Crusaders and the Highlanders and Chiefs will bear heavily on standings.
The Hurricanes will be strengthened by the return of captain Dane Coles, lock Michael Fatialofa and five players, including All Blacks Julian Savea, Cory Jane and Victor Vito who were recently stood down for disciplinary reasons.
Lock Tom Franklin and prop Dan Lienert-Brown return to the Highlanders lineup, bringing it close to full strength.
The Chiefs play the Waratahs in Sydney in a match between the respective leaders of the New Zealand and Australian conferences.