South Africa dropped one place in the overall standings after lifting the Plate in the fourth leg of the IRB Sevens World Series in Wellington, New Zealand, on Saturday.

Having gone unbeaten on the opening day, the BlitzBokke were relegated to the second-tier competition with a 21-5 loss to Fiji in the cup quarterfinals.

They were given a scare in the Plate semifinal, narrowly edging past Canada, but bounced back to thump Tonga in the final.

"I suppose when you lose out in a Cup quarterfinal you've got to maximise your points for the rest of the tournament, and we did that," said SA captain Kyle Brown.

"We had a really tough game against Canada. They're really showing how they're growing every single week, and then we met up with Tonga and played as clinically as we could to win.

"People don't really understand - they'll see these fixtures on the screen like South Africa-Canada and they'll write Canada off, but the way these sides are playing they're hugely competitive now."

Canada struck early, dotting down their first try in the second minute, but South Africa hit back to lead 14-7 at half-time.

The Canadians fought hard, scoring twice in the second period, but the BlitzBokke managed to hold them off for a 21-19 victory.

Cecil Afrika, returning to action after he was rested in the last pool game, scored two tries in the final as Tonga were handed a 24-0 whitewash.

South Africa fell to fourth in the series standings - behind New Zealand, Fiji and England - with 61 points.

The fifth leg, a three-day event, will be held in Las Vegas next week.

"USA Sevens is a good tournament. It's been good to us these last couple of years," Brown said.

"We enjoy playing there so we'll go there now and just try and be as clinical as we have been today."