Four players authored incredible runs in the first month of the year - and it's time to vote for January's WTA Breakthrough of the Month!
Have a look at the nominees and cast your vote before Thursday at 11:59 p.m. ET! The winner will be announced Friday, February 2.
January 2018 WTA Breakthrough of the Month Finalists
Elise Mertens: Mertens began the season by becoming the first woman to win back-to-back titles in at the Hobart International, as she successfully defended her title from last season. She defeated rising Romanian Mihaela Buzărnescu in the final, and doubled up her hadware as she, along with Demi Schuurs, she also won the doubles title.
Mertens next made her main draw debut at the Australian Open and did not lose a set en route to the quarterfinals against Viktoria Kuzmova, No.23 seed Daria Gavrilova, Alizé Cornet and Petra Martic, to reach her first Grand Slam quarterfinal.
In the last eight, Mertens earned her first victory over a Top 5 player as she defeated Elina Svitolina by winning the last seven games, 6-4, 6-0, to reach the semifinals.
With her win over Svitolina, Mertens became the third Belgian woman to reach the last four at the tournament, joining former World No.1s Justine Henin and Kim Clijsters, but saw her run ended by eventual champion Caroline Wozniacki.
Bernarda Pera: The fast-rising American made the most of a second chance in Melbourne, as she was awarded a lucky loser spot in the main draw after losing in the final round of qualifying.
In her Grand Slam singles main draw debut, Pera defeated former junior Wimbledon runner-up Anna Blinkova in the first round before she stunned No.9 seed and former semifinalist Johanna Konta in straight sets in the second round for her first career Top 10 victory.
Though her tournament came to an end at the hands of Barbora Strycova in the third round, Pera improved 12 spots to a career-high No.111 in Monday's rankings as a result.
Hsieh Su-wei: The two-time doubles Grand Slam champion and former World No.1 showed some of the form that took her to a career-high ranking of No.23 in singles four years ago in January.
First, Hsieh reached the semifinals of the ASB Classic in Auckland, her first in nearly two years, by knocking off No.2 seed Strycova en route only to lose out to eventual champion Julia Goerges.
At the Australian Open, she defeated both No.3 seed Garbiñe Muguruza, ending the Spaniard's hopes of rising to World No.1 after the tournament, and 26th seed Agnieszka Radwanska in straight sets to reach the fourth round of a Grand Slam for the second time - matching her career-best performance from a decade earlier in Melbourne.
In the fourth round, she found herself a game away from the quarterfinals against Angelique Kerber, only to fall in a tough three-setter, 4-6, 7-5, 6-2.
Aliaksandra Sasnovich: The Belarusian won a staggering seven straight matches to begin the season at the Brisbane International - with a pair of Top 20 victories - to reach the biggest final of her career at the WTA Premier level event.
Sasnovich defeated Kristina Mladenovic, Anett Kontaveit, Alizé Cornet and Anastasija Sevastova to reach her second final on the WTA in her career - only to see her run stopped by Elina Svitolina.
The 23-year-old remarkably came from a set down in her final qualifying match, and then her first three main draw matches against No.6 seed Mladenovic, Kontaveit and 2017 runner-up Cornet to have the best week of her career so far.
Sasnovich backed up her showing in Brisbane with her first-ever third round appearance at a Grand Slam in Melbourne, before falling to Caroline Garcia in three tough sets.
How it works:
Finalists are selected by wtatennis.com
Winner is then determined by a fan vote on wtatennis.com