SINGAPORE - In their debut at the BNP Paribas WTA Finals Singapore presented by SC Global, Kiki Bertens and Johanna Larsson pulled off a remarkable 7-6(7), 6-7(1), 10-6 quarterfinal upset of No.4 seeds Ashleigh Barty and Casey Dellacqua in one hour and 54 minutes.

In each of the first two sets, it was the Dutch-Swedish duo who fell behind by a break first. Their Australian opponents leapt out to a quick 5-2 lead in the first set, breaking to love in the sixth game and looking every inch like a pair used to playing their best on the big stage.

Ashleigh Barty balances herself for a backhand volley alongside partner Casey Dellacqua (Getty)

However, Bertens and Larsson demonstrated a remarkable resilience over the course of the match, and they hauled their way back to force a tiebreak - in which they would seal the set on their third set point.

It was the Roland Garros runners-up who made the brighter start in the second set, breaking in the first game and holding on to the lead despite a number of thrilling multi-deuce games. Once again, though, this only lasted until the time came for Barty to serve out the set - and once again, the European pair broke back before moving to within a game of taking the match at 6-5.

Kiki Bertens shapes up to hit a forehand volley alongside partner Johanna Larsson (Getty)

When Dellacqua shanked a forehand into the ground at 30-30, it seemed as though the underdogs would have their day - but the Australians gathered themselves. That match point was saved by a crisp Barty volley into the middle of the court and the No.4 seeds dominated the tiebreak, reeling off 10 of the set's last 11 points to force a deciding match tiebreak.

Bertens and Larsson continued to execute their game plan of strong serving backed up by brilliant forecourt play - in particular from the Dutch player, who was a dominant force at net, scything acutely angled backhand volleys with ease. It was Bertens who sealed the upset on her team's second match point by knocking yet another volley past Barty and Dellacqua to set up a semifinal against either Ekaterina Makarova and Elena Vesnina or Gabriela Dabrowski and Xu Yifan.

"In the second set we had one match point and we didn't make it - but we kept on fighting til the end," said Bertens afterwards. "It wasn't that we didn't something bad - they played a really nice point," added Larsson. "We had to focus on the match tiebreak, and we came out swinging pretty good."