convert match points in the third set and was eventually eliminated by the seventh seed and 2014 champion, Grigor Dimitrov, in their second round three-set thriller. As the top seed at the Monterrey Challenger, he won the title beating Aleksandar Vukic in the final. The ATP tour canceled all tournaments from March through July due to the Coronavirus pandemic. When the ATP resumed tournaments in August, Mannarino competed at the Cincinnati Open. He was beaten in the first round by John Millman. Seeded 32nd at the US Open, he made it to the third round where he lost to fifth seed and eventual finalist, Alexander Zverev. In Rome, Mannarino was defeated in the first round by 13th seed Milos Raonic. At the Hamburg Open, he fell in the first round to Dušan Lajović. At the French Open, he suffered a first round loss to Albert Ramos Viñolas. At the St. Petersburg Open, Mannarino was eliminated in the first round by qualifier Ilya Ivashka. Seeded eighth at the first edition of the Bett1Hulks Championship, he reached the quarterfinals where he lost to top seed and eventual champion, Alexander Zverev. Seeded third at the first edition of the Astana Open, he reached the final where he was defeated by fourth seed John Millman. In Paris, he made it to the third round where he fell in a tight three-set match to fourth seed and eventual finalist, Alexander Zverev. Playing his final tournament of the season at the Sofia Open, he reached the semifinal where he lost to Jannik Sinner, who would end up winning the title. Mannarino ended the season ranked 35. 2021: Second Masters 1000 doubles quarterfinal Mannarino started his 2021 season at the Delray Beach Open. Seeded third, he lost in the second round to Cameron Norrie. Seeded 10th at the first edition of the Murray River Open, he was defeated in the second round by Marcos Giron. Seeded 32nd at the Australian Open, he reached the third round where he was eliminated by sixth seed Alexander Zverev. As the top seed at the Singapore Open, Mannarino made it to the quarterfinals where he was beaten by sixth seed Radu Albot. In Rotterdam, he lost in the first round to Hubert Hurkacz; he led 4–1 in the second set and held two set points at 5–4, but he ultimately lost the set and the match. At the Mexican Open, he