Was a history-making effort for Kiki Bertens your biggest breakthrough, of a different sort, in May? Or was a first-time title winner in Yulia Putintseva your pick?
It's time to vote for the Breakthrough of the Month in May!
Have a look at the nominees in the video below and cast your vote for your favorite before voting ends Saturday at 11:59 p.m. ET!
Kiki Bertens: While staking her claim as a nominee for Player of the Month, Bertens broke through the Dutch history books to put herself in contention in this category.
By winning the Mutua Madrid Open, Bertens became the highest-ranking Dutchwoman in history at World No.4.
She passed the mark set by Betty Stove, who reached a career- and country-best ranking of World No.5 in 1977, the year she reached the singles final at Wimbledon.
Marketa Vondrousova: The fast-rising Czech had a week to remember in May in the lead-up to the French Open in Rome.
Vondrousova scored a trio of notable victories, all in three sets, to reach the quarterfinals before losing to eventual runner-up Johanna Konta, also in three sets.
She came from a set down in her first two wins, defeating compatriot Barbora Strycova in the first round, before pulling double duty on the same day later in the tournament due to rain.
She scored her second win of the season over No.3 seed Simona Halep in round two, this time from a set down, and defeated Russian Daria Kasatkina in three long sets later in the day to book her spot in the last eight - the third time in three Premier 5 or Premier Mandatory events this season she'd gone that far.
As a result, she cracked the Top 40 in the rankings for the first time in her career.
Chloe Paquet: Paquet made the most of her time at the Internationaux de Strasbourg on home soil, as she reached her first career WTA semifinal.
The Frenchwoman, who arrived in Strasbourg ranked outside the Top 200, scored three victories before losing to compatriot and eventual runner-up Caroline Garcia in the final four.
She opened her tournament with a win over No.5 seed Sofia Kenin, and followed that up with wins over China's Han Xinyun and former finalist Daria Gavrilova, all of which came in straight sets.
Yulia Putintseva: Putintseva was the latest in a litany of first-time WTA title-winners this season the week before the French Open, winning her first career title on the clay of Nurnberg.
Among her victories on the week was triumphing in what was the longest WTA match of the season to date over Anna-Lena Friedsam in the quarterfinals, and rallying from a set down to defeat Slovenia's Tamara Zidansek in the final.
Who was your Breakthrough of the Month in May? Vote now!