[15] Jannik Sinner 7-5,6-7,4-6 John Isner [26] 2021-08-18 19:35
Stadium: Stadium 3 Round: 25 Ground: Hardcourt outdoor
Home History
| ATP Cincinnati | 2021/08/16 17:15 | Jannik Sinner v Federico Delbonis | 6-2,7-5 |
| ATP Toronto | 2021/08/11 15:00 | James Duckworth v Jannik Sinner | 6-3,6-4 |
| ATP Washington | 2021/08/08 21:00 | Mackenzie McDonald v Jannik Sinner | 5-7,6-4,5-7 |
| ATP Washington | 2021/08/07 20:00 | Jannik Sinner v Jenson Brooksby | 7-6,6-1 |
| ATP Washington | 2021/08/06 19:25 | Jannik Sinner v Steve Johnson | 6-4,6-2 |
| ATP Washington | 2021/08/05 18:00 | Jannik Sinner v Sebastian Korda | 7-6,7-6 |
| ATP Washington | 2021/08/04 20:30 | Jannik Sinner v Emil Ruusuvuori | 6-2,6-4 |
| ATP Atlanta | 2021/07/29 17:30 | Christopher O'Connell v Jannik Sinner | 7-6,6-4 |
Away History
| ATP Cincinnati | 2021/08/17 17:55 | John Isner v Cameron Norrie | 4-6,7-6,6-4 |
| ATP Toronto | 2021/08/15 00:00 | Daniil Medvedev v John Isner | 6-2,6-2 |
| ATP Toronto | 2021/08/14 01:35 | John Isner v Gael Monfils | 7-6,6-4 |
| ATP Toronto | 2021/08/12 16:35 | Andrey Rublev v John Isner | 5-7,6-7 |
| ATP Toronto | 2021/08/11 15:00 | John Isner v Cristian Garin | 4-6,6-3,6-4 |
| ATP Toronto | 2021/08/10 17:25 | John Isner v Alejandro Davidovich Fokina | 6-4,6-1 |
| ATP Atlanta | 2021/08/01 21:00 | Brandon Nakashima v John Isner | 6-7,5-7 |
| ATP Atlanta | 2021/07/31 23:00 | Taylor Fritz v John Isner | 6-7,7-5,3-6 |