Preston's win on Saturday afternoon gave Australia an unassailable 3-0 lead in the qualifying tie.

Australian duo Daria Saville and Ellen Perez made it 4-0 with a 6-3 6-1 win over Jessica Hinojosa Gomez and Maria Navarro in the dead rubber doubles match.

"It was very special to be able to win the tie for Australia to qualify for the finals," Preston said.

"Obviously being able to wear the green and gold it's extremely special for me, and hopefully it's not my (only) time and I get to wear it many more times."

Australia - runner-up twice in the last five years and chasing their first title since 1974 - have booked a spot in November's 12-team finals tournament in Seville.

On Friday, Australia's Arina Rodionova beat the unranked Giuliana Olmos 3-6 6-3 6-1 in just over two hours, before Daria Saville thumped Zacarias 6-1 6-0 in 51 minutes.

Team captain Sam Stosur said Australia displayed great resilience after losing spearhead Storm Hunter to an Achilles tendon rupture on the eve of the tie.

"To win 4-0 is a perfect start for this team this year and I am very proud of all the players," Stosur said.

"We are now in it to try and win it. Now we are there (in the finals) I know every single person on this team will give it everything they have got to try and make it as far as we can."

On Saturday, world No.564 Zacarias rolled her ankle with Preston leading 4-1 in the first set.

The Mexican was at the back of the court writhing in agony after sustaining the injury during a rally.

Zacarias took a medical timeout and showed great courage to return to the match, but struggled to stretch out.

Preston, 18, demonstrated outstanding composure in her debut BJK Cup appearance. The world No.136 lost her opening service game, but then reeled off six consecutive games.

Preston continued on her merry way in the second set to crush her gritty opponent. After Zacarias held her opening service game, the Aussie teenager won the next six games.

"That's how I like to play, aggressively, so even though I lost that first game I was like 'you know it's OK, that's just the first game, there's still so much to go'," Preston said.

"It's definitely not easy to play when you know that the person down the other end isn't at their best.

"I just have to focus on what I'm doing on my side. Obviously that sounds a little harsh, but it's the reality of it. We're in a match."

Preston has high goals for the rest of the year.

"As I start playing high-level tournaments and playing high-ranked opponents everything's going to become a little bit tougher," she said.

"At the moment this is really new for me. I'm learning a lot. It would be great to be able to crack the top 100."

Stosur was thrilled with Preston's display

"What a performance ... incredible for a debut," Stosur said.

"I just said to Taylah, 'we're all behind her, we all believe in you, enjoy the moment, get out here and play the way we know you can play'."

Australian Associated Press