Andrey Rublev began his Dubai Championships title defence by spoiling Filip Krajinovic's birthday when he won 7-5, 6-2.
Krajinovic, who turned 31, raced 5-2 ahead on Monday. The second-seeded Rublev then reeled off 11 of the next 13 games.
Rublev next faces Alejandro Davidovich Fokina, who beat Malek Jaziri in straight sets in the Tunisian's last pro match.
Also, Alexander Zverev beat Jiri Lehecka 4-6, 6-3, 6-4.
Lehecka won their first matchup in January in Sydney, and beat Rublev in Doha last week before blowing five match points against Andy Murray.
Ruud advances
Mexico City: Casper Ruud moved into the second round of the Mexican Open by beating Argentine qualifier Guido Andreozzi 6-4, 4-6, 7-6 (2).
Ruud, who won three titles and reached the French Open and US Open finals in 2022, is playing in Mexico for the second time in his career. Two years ago, he made it to the quarterfinals.
The second-seeded Ruud will next play Taro Daniel, who beat JJ Wolf 6-4, 6-4. Also on Monday, fourth-seeded Holger Rune defeated Ben Shelton 6-7 (7), 6-4, 6-2 and will next face either Nuno Borges or Nick Chapell. Taylor Fritz, Tommy Paul, Denis Shapovalov, Michael Mmoh, Feliciano Lopez and Francis Tiafoe also won.