Canada will have to wait one more day to see if it can secure a spot in the Davis Cup World Group.

Canada missed a chance to clinch its tie with South Africa on Saturday, falling in straight sets in doubles competition.

Izak van der Merwe and Raven Klaasen defeated Toronto's Daniel Nestor and Vancouver's Vasek Pospisil 6-4, 7-6, 7-6 to earn South Africa's first win in the best-of-five series at Uniprix Stadium.

"South Africa was in a position where they absolutely had to win and that seemed to give them a lift to take their game to the next level, which they did very well," Canada captain Martin Laurendeau said. "They played desperate, they played to win and they played very solid. They were consistent from start to finish, served and returned well. We weren't.

"We expected a tough match, maybe not a loss but a tough match nonetheless and we got exactly that."

The visitors, who have been playing with an injury-depleted roster, clinched their first set win of the tie by rallying from a 4-3 deficit with three straight game wins.

Nestor and Pospisil seemed to be on their way to evening up the sets at one apiece, leading 5-2 through seven games. But van der Merwe and Klaasen began their comeback.

After holding serve in the eighth game, the South African pair benefited from three double faults by Canada to cut the lead to 5-4. The Canadians recorded eight of their 10 double faults in the second set.

"They were more solid, obviously. Too many missed returns, not enough first serves — I think those were the biggest points," said a noticeably disappointed Nestor.

South Africa then held serve to even up the set 5-5 before Canada reclaimed the lead. But van der Merwe and Klaasen tied the set again and won the tiebreaker 7-3.

"We wanted to really make these guys play and work for every point. We knew that we weren't going to get a lot of opportunity and the opportunities that we do get, to execute them. That's exactly what they did — they took every opportunity they got," said South Africa captain John-Laffnie de Jager.

Canada trailed the third set 5-2 before reeling off three straight wins to tie it at 5-5.

Van der Merwe held serve to take the lead but Canada did the same to knot it up, 6-6.

Nestor and Pospisil pulled themselves into a tie twice in the tiebreaker before eventually losing 7-5.

"When you're up two sets-love you never want to keep that door open for your opponent. Playing singles tomorrow or not, it's key," van der Merwe said. "That's why we stayed positive even though we didn't close out the (third) set when we could."

Canada needs just one win in Sunday's two singles rubber matches to stay in the World Group. Favoured overall heading into the tournament, Canada will be especially so on the final day with Milos Raonic scheduled to hit the court in the opening match, against van der Merwe.

"These guys are competitors. They want to win everything, from soccer games to card games to this match. Obviously this defeat hurts because they wanted to seal the deal and they couldn't do it," Laurendeau said. "We have to digest this loss but briefly because we're still up 2-1. We've got two more shots at it tomorrow, starting with our top player in the first match of the day.

"We just have to stay calm and regroup and not lose sight of the position that we're in, which is a good one."

Pospisil and Nikala Scholtz are slated to face off in the fifth and final match.