# 2021 Kremlin Cup – Men's singles

Andrey Rublev was the reigning champion from when the tournament was last held in 2019, but lost to Adrian Mannarino in the second round in a rematch of the 2019 final.
Aslan Karatsev won the title, defeating Marin Čilić in the final, 6–2, 6–4.

## Seeds

The top four seeds received a bye into the second round.
* Andrey Rublev (second round)
* Aslan Karatsev (champion)
* Karen Khachanov (semifinals)
* Filip Krajinović (second round)
* Alexander Bublik (first round)
* Marin Čilić (final)
* Ilya Ivashka (withdrew)
* Laslo Đere (first 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 | Final | Final | Final | Final |
| LL | Ričardas Berankis | 3 | 4 | | | | |
| 6 | Marin Čilić | 6 | 6 | | | | |
| 6 | Marin Čilić | 6 | 6 | 6 | Marin Čilić | 2 | 4 |
| | | | | 2 | Aslan Karatsev | 6 | 6 |
| 3 | Karen Khachanov | 6$^7$ | 1 | 2 | Aslan Karatsev | 6 | 6 |
| 2 | Aslan Karatsev | 7$^9$ | 6 | | | | |

### Top half

| First round | 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 |
| | | | | | 1 | A Rublev | 7 | 6$^4$ | 3 | | | | | | | | |
| WC | R Safiullin | 6 | 6$^6$ | 4 | | A Mannarino | 5 | 7$^7$ | 6 | | | | | | | | |
| | A Mannarino | 1 | 7$^8$ | 6 | | | | | | | A Mannarino | 2 | 6$^1$ | | | | |
| | F Coria | 6 | 5 | 6 | | | | | | LL | R Berankis | 6 | 7$^7$ | | | | |
| WC | A Kachmazov | 2 | 7 | 2 | | F Coria | 2 | 1 | | | | | | | | | |
| WC | E Donskoy | 1 | 3 | | LL | R Berankis | 6 | 6 | | | | | | | | | |
| LL | R Berankis | 6 | 6 | | | | | | | | | | | LL | R Berankis | 3 | 4 |
| | | | | | | | | | | | | | | 6 | M Čilić | 6 | 6 |
| | | | | | 4 | F Krajinović | 3 | 4 | | | | | | | | | |
| PR | G Pella | 2 | 0$^r$ | | | P Martínez | 6 | 6 | | | | | | | | | |
| | P Martínez | 6 | 0 | | | | | | | | P Martínez | 1 | 2 | | | | |
| | T Paul | 7$^9$ | 7 | | | | | | | 6 | M Čilić | 6 | 6 | | | | |
| | M Ymer | 6$^7$ | 5 | | | T Paul | 5 | 3 | | | | | | | | | |
| Q | D Džumhur | 7$^7$ | 1 | 1 | 6 | M Čilić | 7 | 6 | | | | | | | | | |
| 6 | M Čilić | 6$^4$ | 6 | 6 | | | | | | | | | | | | | |

### Bottom half

| First round | 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 |
| 5 | A Bublik | 4 | 3 | | | | | | | | | | | | | | |
| Q | I Marchenko | 6 | 6 | | Q | I Marchenko | 1 | 7 | 4 | | | | | | | | |
| | J Millman | 6$^5$ | 6 | 6 | | J Millman | 6 | 5 | 6 | | | | | | | | |
| | B Bonzi | 7$^7$ | 4 | 3 | | | | | | | J Millman | 5 | 6$^4$ | | | | |
| | J Duckworth | 3 | 7 | 6 | | | | | | 3 | K Khachanov | 7 | 7$^7$ | | | | |
| Q | B Gojo | 6 | 5 | 2 | | J Duckworth | 6 | 3 | 1 | | | | | | | | |
| | | | | | 3 | K Khachanov | 3 | 6 | 6 | | | | | | | | |
| | | | | | | | | | | | | | | 3 | K Khachanov | 6$^7$ | 1 |
| 8 | L Đere | 7$^7$ | 5 | 3 | | | | | | | | | | 2 | A Karatsev | 7$^9$ | 6 |
| PR | G Simon | 6$^3$ | 7 | 6 | PR | G Simon | 6 | 6 | | | | | | | | | |
| | M McDonald | 6 | 6 | | | M McDonald | 3 | 2 | | | | | | | | | |
| | Y Nishioka | 3 | 4 | | | | | | | PR | G Simon | 4 | 3 | | | | |
| | M Kecmanović | 3 | 6 | 4 | | | | | | 2 | A Karatsev | 6 | 6 | | | | |
| Q | E Gerasimov | 6 | 1 | 6 | Q | E Gerasimov | 4 | 3 | | | | | | | | | |
| | | | | | 2 | A Karatsev | 6 | 6 | | | | | | | | | |

## Qualifying
### Seeds

* Egor Gerasimov (qualified)
* Ričardas Berankis (qualifying competition, lucky loser)
* Radu Albot (first round)
* Damir Džumhur (qualified)
* Jurij Rodionov (qualifying competition)
* Zdeněk Kolář (qualifying competition)
* Marc Polmans (first round)
* Elias Ymer (qualifying competition)

### Qualifiers

* Egor Gerasimov
* Borna Gojo
* Illya Marchenko
* Damir Džumhur

### Lucky loser

* Ričardas Berankis

### Qualifying draw
#### First qualifier

| First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 1 | Egor Gerasimov | 6 | 6 | | | | | |
| | Ramkumar Ramanathan | 3 | 4 | | | | | |
| | Ramkumar Ramanathan | 3 | 4 | 1 | Egor Gerasimov | 6 | 1 | 6 |
| | | | | 8 | Elias Ymer | 4 | 6 | 2 |
| Alt | Pavel Kotov | 2 | 3 | 8 | Elias Ymer | 4 | 6 | 2 |
| 8 | Elias Ymer | 6 | 6 | | | | | |

#### Second qualifier

| First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 2 | Ričardas Berankis | 6 | 6 | | | | | |
| | Dmitry Popko | 4 | 1 | | | | | |
| | Dmitry Popko | 4 | 1 | 2 | Ričardas Berankis | 6 | 5 | 4 |
| | | | | | Borna Gojo | 4 | 7 | 6 |
| | Borna Gojo | 7$^7$ | 6 | | Borna Gojo | 4 | 7 | 6 |
| 7 | Marc Polmans | 6$^5$ | 2 | | | | | |

#### Third qualifier

| First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 3 | Radu Albot | 6$^5$ | 3 | | | | |
| | Illya Marchenko | 7$^7$ | 6 | | | | |
| | Illya Marchenko | 7$^7$ | 6 | | Illya Marchenko | 6 | 6 |
| | | | | 5 | Jurij Rodionov | 4 | 1 |
| PR | Denis Istomin | 4 | 2 | 5 | Jurij Rodionov | 4 | 1 |
| 5 | Jurij Rodionov | 6 | 6 | | | | |

#### Fourth qualifier

| First round | First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 4 | Damir Džumhur | 6$^9$ | 6 | 6 | | | | |
| WC | Maxim Zhukov | 7$^{11}$ | 0 | 4 | | | | |
| WC | Maxim Zhukov | 7$^{11}$ | 0 | 4 | 4 | Damir Džumhur | 7 | 6 |
| | | | | | 6 | Zdeněk Kolář | 5 | 3 |
| WC | Yaroslav Demin | 4 | 2 | | 6 | Zdeněk Kolář | 5 | 3 |
| 6 | Zdeněk Kolář | 6 | 6 | | | | | |