Birmingham, UK, 25 June 2017 | Matt Trollope

What a season Ash Barty is having.

The talented Australian, just 21 years of age, weathered an early storm from Garbine Muguruza to beat the Spaniard 3-6 6-4 6-3, advancing to the WTA Birmingham final.

It’s her second final of the season – but first on grass, and first at WTA Premier level – and there she’ll meet Czech Petra Kvitova, who earlier on Saturday got past injured compatriot Lucie Safarova.

“It’s fantastic to have (Petra) back on the court. She’s one of the nicest girls and we really missed her,” Barty said.

The 14th-ranked Muguruza is the biggest scalp of Barty’s career, and an even more significant one given the 2016 Roland Garros champion was ranked as high as No.2 this time last year.

Muguruza was also a Wimbledon finalist in 2015 and, when at her peak, is widely regarded as one of the best players on the women’s tour.

Yet Barty could well be developing a similar reputation, especially on grass.

“It’s really cool (to reach the final)! It was nice to be able to come out and execute what we wanted to do, and to win is a bonus,” Barty said.

“Garbine is a quality player and been in this situation a lot of times.”

The Aussie played an exquisite match perfectly suited to the surface, throwing in plenty of slices and attacking as soon as she had an opening to exploit the quick, slick surface.

Leading 3-2 in the first set, Barty watched as the Spaniard clicked into gear and reeled off five straight games to take command of the match.

The Queenslander called coach Craig Tyzzer onto the court after the first set for a consultation; Tyzzer implored her to improve her first serve percentage and get Muguruza moving laterally, as she was struggling to push the powerful Spaniard back off the baseline.

Barty must have listened; she landed 72 per cent of her first serves in set two (compared to less than half in the opening set) and loosened up on her groundstrokes, frequently beating Muguruza with pace and placement off her forehand wing.

She broke serve in the seventh game of the second set, and from there quickly sent the match into a third.

Muguruza collapsed, struggling to find the court with her powerful bombs and soon slumping behind 1-5. But she was being forced to go for too much against the Australian, who frustrated Muguruza with a clever mix of heavy forehands, off-paced low slices and impressive defence.

The sixth seed staved off two match points in the seventh game and broke a suddenly error-prone Barty to tighten up the score at 5-3.

But in the ninth game, Barty quickly arrived at match point after more errors from Muguruza and sealed a famous victory with a backhand winner.

Barty is also through to the doubles final with compatriot Casey Dellacqua; they advanced when CoCo Vandeweghe withdrew prior to their semifinal.

In the previous round, Barty and Dellacqua beat Muguruza and Dominika Cibulkova, perhaps a sign of what was to come for Barty in singles on Saturday.

The Aussie combo in the final will face either Chan Hao-Ching and Zhang Shuai or American pairing Rachel Atawo and Chrisina McHale.