Tennis Tracker: Sinner and Rune through in Cincinnati, Montreal champion Popyrin dumped out
23:05 CET - Pablo Carreno-Busta (33) has secured his highest-ranked win since 2022, beating Sebastian Korda (24) 7-5, 6-1.
22:46 CET - Mirra Andreeva (17) secured a really impressive win over Emma Navarro (23), crushing her American opponent 6-2, 6-2 in a little over an hour.
22:24 CET - Just days after his shock Masters victory in Montreal, Alexei Popyrin (25) has fallen 5-7, 3-6 to veteran Frenchman Gael Monfils (37).
22:12 CET - Brit Jack Draper (22) surived an almighty challenge from Jaume Munar (27), eventually snatching a 7-5, 3-6, 7-6(5) victory.
Liudmila Samsonova (25) had it far easier, beating Xinyu Wang (22) 6-4, 6-4 in an hour and a half.
21:26 CET - World No.1 Jannik Sinner (22) was nowhere near his best, but the Italian still moved into the second round of Cincinnati with a testing 6-4, 7-5 win over American Alex Michelsen (19).
20:36 CET - In one of the heavyweight clashes of the first round, Holger Rune (21) overcame Matteo Berrettini (28) 2-6, 6-1, 6-4.
20:22 CET - Leylah Fernandez (21) didn't have it all her own way, but in the end, the Canadian came from a set behind to beat Yue Yuan (25) 3-6, 6-4, 6-3.
19:19 CET - Stefanos Tsitsipas (26) battled from a set and a break down to overcome Jan-Lennard Struff (34) 4-6, 6-4, 6-3, but the Greek looked far from convincing against his German opponent.
Anna Kalinskaya (25) also fought back against Katerina Siniakova (28), winning 1-6, 6-2, 6-3. The Russian will be hoping to stay fit in Cincinnati after suffering an injury in Toronto last week.
18:41 CET - Felix Auger-Aliassime (24) and Paula Badosa (26) have both claimed straight-set victories, moving into the second round of Cincinnati.
18:05 CET - The first winner of the day in Cincinnati is Diana Shnaider (20), who coasted past Shuai Zhang (35) 6-1, 6-4. The Russian is having a fabulous 2024, and will be looking to build on her semi-final run in Canada last week.
15:50 CET - We're just over an hour away until play starts in Cincinnati, with Jannik Sinner (22), Stefanos Tsitsipas (26), Anna Kalinskaya (25) and Diana Shnaider (20) all taking to the court in the early evening.
Follow the full men's draw here and the women's draw here.
09:48 CET - Before we look ahead to today's play which gets underway around 17:00 CET, there are a few notable results to bring you from overnight.
Home favourite Taylor Fritz (26) was dumped out by compatriot Brandon Nakashima (23) 6-4, 4-6, 7-6(4), while Lorenzo Musetti (22) battled past Nicolas Jarry (28) in three tight sets.
Meanwhile, on the women's side of the draw, Ashlyn Krueger (20) shocked the in-form Donna Vekic (28) 5-7, 7-6(4), 6-2 and Elina Svitolina (29) recovered from a set down to defeat Yafan Wang (30) 5-7, 6-3, 6-2.
Check out the full men's schedule here and the women's schedule here.
09:00 CET - Good morning and welcome to our coverage of today's tennis action!