ATP 250 · 2021-10-25 · draw of 32
St. Petersburg 2021
HardFinal
| 🇭🇷 Marin Cilic | d. | 🇺🇸 Taylor Fritz | 7-6(3) 4-6 6-4 | H2H |
Semifinals
| 🇭🇷 Marin Cilic | d. | 🇳🇱 Botic van de Zandschulp | 6-3 6-3 | H2H |
| 🇺🇸 Taylor Fritz | d. | 🇩🇪 Jan-Lennard Struff | 5-7 6-1 6-3 | H2H |
Quarterfinals
| 🇳🇱 Botic van de Zandschulp | d. | 🇷🇺 Andrey Rublev | 6-3 6-4 | H2H |
| 🇭🇷 Marin Cilic | d. | 🇪🇸 Roberto Bautista Agut | 6-4 3-6 6-3 | H2H |
| 🇺🇸 Taylor Fritz | d. | 🇦🇺 John Millman | 6-4 6-2 | H2H |
| 🇩🇪 Jan-Lennard Struff | d. | 🇨🇦 Denis Shapovalov | 6-4 6-3 | H2H |
Round of 16
| 🇷🇺 Andrey Rublev | d. | 🇧🇾 Ilya Ivashka | 6-4 6-4 | H2H |
| 🇳🇱 Botic van de Zandschulp | d. | 🇺🇸 Sebastian Korda | 6-2 7-5 | H2H |
| 🇪🇸 Roberto Bautista Agut | d. | 🇺🇸 Mackenzie McDonald | 6-3 6-2 | H2H |
| 🇭🇷 Marin Cilic | d. | 🇷🇺 Karen Khachanov | 6-4 6-7(1) 6-4 | H2H |
| 🇺🇸 Taylor Fritz | d. | 🇺🇸 Tommy Paul | 7-6(3) 6-4 | H2H |
| 🇦🇺 John Millman | d. | 🇷🇺 Aslan Karatsev | 6-3 6-2 | H2H |
| 🇩🇪 Jan-Lennard Struff | d. | 🇰🇿 Alexander Bublik | 6-4 6-3 | H2H |
| 🇨🇦 Denis Shapovalov | d. | 🇪🇸 Pablo Andujar | 2-6 6-3 6-0 | H2H |
Round of 32
| 🇧🇾 Ilya Ivashka | d. | 🇷🇸 Laslo Djere | 6-3 6-2 | H2H |
| 🇳🇱 Botic van de Zandschulp | d. | 🇯🇵 Yoshihito Nishioka | 6-2 6-2 | H2H |
| 🇺🇸 Sebastian Korda | d. | 🇭🇷 Nino Serdarusic | 7-6(2) 7-5 | H2H |
| 🇺🇸 Mackenzie McDonald | d. | 🇧🇾 Egor Gerasimov | 7-5 6-4 | H2H |
| 🇭🇷 Marin Cilic | d. | 🇪🇸 Albert Ramos-Vinolas | 6-2 6-3 | H2H |
| 🇷🇺 Karen Khachanov | d. | 🇫🇷 Adrian Mannarino | 6-3 6-3 | H2H |
| 🇺🇸 Taylor Fritz | d. | 🇫🇮 Emil Ruusuvuori | 6-1 6-4 | H2H |
| 🇺🇸 Tommy Paul | d. | 🇪🇸 Pedro Martinez | 6-3 6-2 | H2H |
| 🇦🇺 John Millman | d. | 🇮🇱 Yshai Oliel | 6-1 6-1 | H2H |
| 🇰🇿 Alexander Bublik | d. | 🇷🇺 Evgenii Tiurnev | 6-3 6-4 | H2H |
| 🇩🇪 Jan-Lennard Struff | d. | 🇦🇺 James Duckworth | 7-6(3) 6-3 | H2H |
| 🇪🇸 Pablo Andujar | d. | 🇦🇷 Federico Delbonis | 6-2 7-6(1) | H2H |