title: 2021 St. Petersburg Open – Singles
text: # 2021 St. Petersburg Open – Singles
  
  Andrey Rublev was the defending champion, but lost in the quarterfinals to Botic van de Zandschulp.
  
  Marin Čilić won the title, defeating Taylor Fritz in the final, $7–6^{(7–3)},$ 4–6, 6–4.
  
  ## Seeds
  
  The top four seeds received a bye into the second round.
  
  * Andrey Rublev (quarterfinals)
  * Denis Shapovalov (quarterfinals)
  * Roberto Bautista Agut (quarterfinals)
  * Aslan Karatsev (second round)
  * Taylor Fritz (final)
  * Karen Khachanov (second round)
  * Alexander Bublik (second round)
  * Sebastian Korda (second round)
  
  ## Draw
  
  ### Key
  
  * Q = Qualifier
  * WC = Wild card
  * LL = Lucky loser
  * Alt = Alternate
  * SE = Special exempt
  * PR = Protected ranking
  * ITF = ITF entry
  * JE = Junior exempt
  * w/o = Walkover
  * r = Retired
  * d = Defaulted
  * SR = Special ranking
  
  ### Finals
  
  | Semifinals | Semifinals | Semifinals | Semifinals | Semifinals | Final | Final | Final | Final | Final |
  | - | - | - | - | - | - | - | - | - | - |
  | Q | Botic van de Zandschulp | 3 | 3 | | | | | | |
  | | Marin Čilić | 6 | 6 | | | | | | |
  | | Marin Čilić | 6 | 6 | | | Marin Čilić | $7^7$ | 4 | 6 |
  | | | | | | 5 | Taylor Fritz | $6^3$ | 6 | 4 |
  | 5 | Taylor Fritz | 5 | 6 | 6 | 5 | Taylor Fritz | $6^3$ | 6 | 4 |
  | | Jan-Lennard Struff | 7 | 1 | 3 | | | | | |
  
  ### Top half
  
  | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals |
  | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - |
  | | | | | 1 | A Rublev | 6 | 6 | | | | | | | | | | |
  | | L Đere | 3 | 2 | | I Ivashka | 4 | 4 | | | | | | | | | | |
  | | I Ivashka | 6 | 6 | | | | | | 1 | A Rublev | 3 | 4 | | | | | |
  | Q | B van de Zandschulp | 6 | 6 | | | | | | Q | B van de Zandschulp | 6 | 6 | | | | | |
  | Q | Y Nishioka | 2 | 2 | Q | B van de Zandschulp | 6 | 7 | | | | | | | | | | |
  | WC | N Serdarušić | $6^2$ | 5 | 8 | S Korda | 2 | 5 | | | | | | | | | | |
  | 8 | S Korda | $7^7$ | 7 | | | | | | | | | | | Q | B van de Zandschulp | 3 | 3 |
  | | | | | | | | | | | | | | | | M Čilić | 6 | 6 |
  | | | | | 3 | R Bautista Agut | 6 | 6 | | | | | | | | | | |
  | Q | E Gerasimov | 5 | 4 | | M McDonald | 3 | 2 | | | | | | | | | | |
  | | M McDonald | 7 | 6 | | | | | | 3 | R Bautista Agut | 4 | 6 | 3 | | | | |
  | | M Čilić | 6 | 6 | | | | | | | M Čilić | 6 | 3 | 6 | | | | |
  | | A Ramos Viñolas | 2 | 3 | | M Čilić | 6 | $6^1$ | 6 | | | | | | | | | |
  | | A Mannarino | 3 | 3 | 6 | K Khachanov | 4 | $7^7$ | 4 | | | | | | | | | |
  | 6 | K Khachanov | 6 | 6 | | | | | | | | | | | | | | |
  
  ### Bottom half
  
  | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals | Semifinals |
  | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - |
  | 5 | T Fritz | 6 | 6 | | | | | | | | | | | | | | |
  | Q | E Ruusuvuori | 1 | 4 | 5 | T Fritz | $7^7$ | 6 | | | | | | | | | | |
  | | P Martínez | 3 | 2 | | T Paul | $6^3$ | 4 | | | | | | | | | | |
  | | T Paul | 6 | 6 | | | | | | 5 | T Fritz | 6 | 6 | | | | | |
  | | J Millman | 6 | 6 | | | | | | | J Millman | 4 | 2 | | | | | |
  | WC | Y Oliel | 1 | 1 | | J Millman | 6 | 6 | | | | | | | | | | |
  | | | | | 4 | A Karatsev | 3 | 2 | | | | | | | | | | |
  | | | | | | | | | | | | | | 5 | T Fritz | 5 | 6 | 6 |
  | 7 | A Bublik | 6 | 6 | | | | | | | | | | | J-L Struff | 7 | 1 | 3 |
  | WC | E Tiurnev | 3 | 4 | 7 | A Bublik | 4 | 3 | | | | | | | | | | |
  | | J-L Struff | $7^7$ | 6 | | J-L Struff | 6 | 6 | | | | | | | | | | |
  | | J Duckworth | $6^3$ | 3 | | | | | | | J-L Struff | 6 | 6 | | | | | |
  | | F Delbonis | 2 | $6^1$ | | | | | | 2 | D Shapovalov | 4 | 3 | | | | | |
  | PR | P Andújar | 6 | $7^7$ | PR | P Andújar | 6 | 3 | 0 | | | | | | | | | |
  | | | | | 2 | D Shapovalov | 2 | 6 | 6 | | | | | | | | | |
  
  ## Qualifying
  
  ### Seeds
  
  * Botic van de Zandschulp (qualified)
  * Benjamin Bonzi (first round)
  * Federico Coria (first round)
  * Miomir Kecmanović (qualifying competition)
  * Emil Ruusuvuori (qualified)
  * Yoshihito Nishioka (qualified)
  * Mikael Ymer (first round)
  * Egor Gerasimov (qualified)
  
  ### Qualifiers
  
  * Botic van de Zandschulp
  * Emil Ruusuvuori
  * Egor Gerasimov
  * Yoshihito Nishioka
  
  ### Qualifying draw
  
  **First qualifier**
  
  | First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
  | - | - | - | - | - | - | - | - | - |
  | 1 | Botic van de Zandschulp | 6 | | | | | | |
  | Alt | Marc Polmans | $6^r$ | | | | | | |
  | Alt | Marc Polmans | $6^r$ | | 1 | Botic van de Zandschulp | 5 | 6 | 6 |
  | | | | | Alt | Evgeny Donskoy | 7 | 3 | 2 |
  | Alt | Evgeny Donskoy | 6 | 7 | Alt | Evgeny Donskoy | 7 | 3 | 2 |
  | 7 | Mikael Ymer | 2 | 5 | | | | | |
  
  **Second qualifier**
  
  | First round | First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
  | - | - | - | - | - | - | - | - | - |
  | 2 | Benjamin Bonzi | 6 | $6^4$ | 2 | | | | |
  | WC | Dmitry Popko | 4 | $7^7$ | 6 | | | | |
  | WC | Dmitry Popko | 4 | $7^7$ | 6 | WC | Dmitry Popko | $6^2$ | 4 |
  | | | | | | 5 | Emil Ruusuvuori | $7^7$ | 6 |
  | PR | Gilles Simon | 0 | 3 | | 5 | Emil Ruusuvuori | $7^7$ | 6 |
  | 5 | Emil Ruusuvuori | 6 | 6 | | | | | |
  
  **Third qualifier**
  
  | First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
  | - | - | - | - | - | - | - | - |
  | 3 | Federico Coria | 3 | 4 | | | | |
  | | Radu Albot | 6 | 6 | | | | |
  | | Radu Albot | 6 | 6 | | Radu Albot | $6^2$ | 4 |
  | | | | | 8 | Egor Gerasimov | $7^7$ | 6 |
  | | Damir Džumhur | 1 | $6^6$ | 8 | Egor Gerasimov | $7^7$ | 6 |
  | 8 | Egor Gerasimov | 6 | $7^8$ | | | | |
  
  **Fourth qualifier**
  
  | First round | First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
  | - | - | - | - | - | - | - | - | - | - |
  | 4 | Miomir Kecmanović | 2 | 6 | 6 | | | | | |
  | WC | Evgeny Karlovskiy | 6 | 4 | 1 | | | | | |
  | WC | Evgeny Karlovskiy | 6 | 4 | 1 | 4 | Miomir Kecmanović | 3 | 6 | 2 |
  | | | | | | 6 | Yoshihito Nishioka | 6 | 4 | 6 |
  | Alt | Roman Safiullin | 5 | 2 | | 6 | Yoshihito Nishioka | 6 | 4 | 6 |
  | 6 | Yoshihito Nishioka | 7 | 6 | | | | | | |
  