The mad scramble for Super 14 playoff spots continues on Friday when round 12 of world rugby's most cut-throat tournament kicks off with a blockbuster in Christchurch.

The showdown between the table-topping Crusaders and third-placed Sharks at Jade Stadium will set the scene for another intriguing weekend of action in which all but one of the seven fixtures will have a direct bearing on the make-up of this season's semi-finalists.

Barring a colossal reversal of form, the six-time Super champion Crusaders appear the only team certain of making the playoffs with three rounds of the regular season remaining.

The Crusaders are six competition points clear of the second-placed Waratahs and will clinch the minor premiership - as well as bump the faltering Sharks out of the top four for the first time all season - if they preserve their unbeaten record at home this campaign.

Runners-up last year to South African rivals the Bulls, the Sharks opened 2008 with a blaze of glory, winning seven of their first eight games and drawing the other, before falling in a hole.

Back-to-back losses in Australia to the Brumbies and Waratahs have left the Sharks on the brink, with the Chiefs, Stormers and Brumbies all positioned to capitalise on another failure and leapfrog the Durbanites on the most congested of competition tables.

The Waratahs will be gunning for a franchise-best sixth successive victory when they tackle the Bulls in Pretoria on Saturday.

The Waratahs left for South Africa full of confidence and believing one win in the republic, over either the Bulls or next week against the Stormers, will probably be enough to confirm their participation in the semi-finals.

Skipper Phil Waugh, who has been instrumental in his side's surge up the ladder, said two wins in South Africa might even be enough for the fast-finishing Waratahs to host a playoff.

The most pleasing thing for Waugh, though, is that the Waratahs are peaking perfectly for the business end of the season.

"You want to be playing your best football at this time of the year and progressing even more I suppose," Waugh said.

"In the past, we've been criticised for peaking too early and falling off later in the season. We're hoping to turn that around.

"Our form wasn't great at the front end of the season, so I guess there was only one way to go and it seems the passes are starting to stick.

"And one of the great things is having combinations in selection and that's allowed good continuity and guys are playing well together.

"So that obviously adds to the cohesion in the team."

A hat-trick of victories have revived the Brumbies' final hopes and Stirling Mortlock's team will continue their sudden-death run against the Stormers in Cape Town early Sunday morning AEST.

So desperately tight is the race to the finals that another win could propel the Brumbies as high as third - but a loss would probably extinguish their title chances.

Of the other Australian teams, even the ninth-placed Western Force remain a mathematical chance of squeezing into the playoffs.

But they probably need three successive bonus-point triumphs, starting with a big home win over the high-flying Chiefs in Perth on Saturday night.

The Chiefs are aiming for their sixth straight win.

In other games, the Queensland Reds have the opportunity to put the Blues out of their misery in Brisbane on Friday night, the Hurricanes tackle the Lions in Wellington on Saturday and the Cheetahs and Highlanders clash in Bloemfontein on Sunday morning (AEST) in the only game with no bearing on the semi-finals.

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