Five players finished the summer hard court season with the best results of their career, but only one will be crowned your Breakthrough of the Month for August.

Have a look at the nominees and cast your vote before Thursday at 11:59 p.m. ET! The winner will be announced Friday, September 14.

August 2018 WTA Breakthrough of the Month Finalists

Marketa Vondrousova: The Czech teenager reached the second week of a Grand Slam for the first time in her career at the US Open.

The beneficiary of a withdrawal by her first round foe, No. 31 seed Mihaela Buzarnescu, meant that Vondrousova took on a lucky loser in Mona Barthel in the opening round, helping the Czech earn her first Grand Slam victory since January's Australian Open. 

From there, she defeated former Wimbledon finalist Eugenie Bouchard and Cincinnati champion and No. 13 seed Kiki Bertens to have the best major result of her young career to date.

Aryna Sabalenka: The Belarusian had herself a searing summer, reaching the third round in Montreal and the semifinals in Cincinnati before winning her first career title in New Haven during the US Open Series.

In Montreal, Sabalenka saved multiple match points in a dramatic second round victory over Caroline Wozniacki, the first of five Top 10 victories she tallied in the month.

Wins over Karolina Pliskova and Caroline Garcia followed in Cincinnati, and another win over World No. 9 Julia Goerges came in the semifinals of New Haven, before she defeated Carla Suárez Navarro to win her first-ever singles title.

Sabalenka's form continued into the US Open, where she scored another upset over two-time Wimbledon champion Petra Kvitova in the third round, and became the only player to take a set from eventual champion Naomi Osaka in an eventual fourth round defeat. 

Lesia Tsurenko: The 29-year-old Ukrainian No.2 had some of her best career results this summer, culminating with a major breakout in New York. 

At the Western & Southern Open in Cincinnati, Tsurenko upset defending champion Garbiñe Muguruza for her first Top 10 victory in three years before eventually falling to World No. 1 Simona Halep in the last eight.

At the US Open, Tsurenko's big wins continued, as she snapped an 0-9 streak against players ranked in the Top 5 with a second round win over Australian Open champion Caroline Wozniacki. 

Later, she rallied from a set and a break down in searing conditions to defeat Vondrousova in the round of 16, before falling to eventual champion Naomi Osaka in the last eight. 

Ashleigh Barty: The Aussie had herself a consistent summer, which was highlighted by a semifinal showing in Montreal, and her first-ever appearance in the second week of a Grand Slam.

In Montreal, Barty scored wins over Irina-Camelia Begu, Alison van Uytvanck, Alizé Cornet and Bertens before being stopped by eventual champion and World No.1 Simona Halep.

Halep again stopped her campaign in Cincinnati, after she scored wins over Vondrousova and Kaia Kanepi - who upset Halep in the first round of the US Open and reached the fourth round just about two weeks later.

In New York, Barty arrived as the No.18 seed and scored straight set victories over Ons Jabeur, Lucie Safarova and Karolina Muchova before falling to Karolina Pliskova in her best-ever major result. 

Anastasija Sevastova: The Latvian lived up to her reputation as a US Open giant-killer, as she reached the final four of a Grand Slam for the first time in her career in New York.

Sevastova scored two Top 10 victories over the fortnight, against Elina Svitolina and defending champion Sloane Stephens - with the latter coming in her third straight quarterfinal showing at the year's final Grand Slam. 

Who had the Breakthrough of the Month in August? Vote now!

How it works:

Finalists are selected by wtatennis.com
Winner is then determined by a fan vote on wtatennis.com

Previous WTA Breakthroughs of the Month for 2018
January: Hsieh Su-wei
February: Daria Kasatkina
March: Danielle Collins
April: Ana Bogdan
May: Mihaela Buzarnescu
June: Tatjana Maria
July: Wang Qiang