Qatar Open champion Elise Mertens has been upset 5-7 6-4 7-5 by Chinese qualifier Zhu Lin after a battle lasting nearly three hours in the first round of the Dubai Duty Free Tennis Championships.
Mertens, the 16th seed, started poorly on Monday but rallied to win the first set before Zhu struck back, opening a 5-1 lead in the second only for the Belgian to reel her in and get back on serve.
However, Zhu held her nerve, claiming the second set to send the match to a decider and recovering from a 3-1 deficit in the third to seal the biggest victory of her career and set up a second round clash with Ukrainian Lesia Tsurenko.
Tunisia's Ons Jabeur will face holder Elina Svitolina in the next round after defeating Croatia's Donna Vekic 6-4 7-6 (11-9), while qualifier Jennifer Brady beat former French Open champion Jelena Ostapenko 6-4 6-0.
Brady was one of three Americans to advance on the second day of the tournament, with her compatriots Alison Riske and Sofia Kenin also reaching the next round.
Kenin turned in a dominant performance to get past Romanian Mihaela Buzarnescu 6-3 6-0, while Riske stunned 13th seed Julia Goerges 6-4 7-5 to set up a meeting with former finalist Alize Cornet of France.
China's Shuai Zhang continued the trend of upsets when she beat 15th seed Anett Kontaveit 7-6 (7-3) 6-3.
But the biggest name to exit the tournament bowed out without playing a shot. Caroline Wozniacki, the ninth seed, withdrew just before her opener after failing to shake off the virus that kept her out of the Qatar Open last week.
The Dane's place in the draw was taken by lucky loser Polona Hercog, who was sent packing by Switzerland's Stefanie Voegele in straight sets.
