# 2021 Nur-Sultan Challenger II – Singles

This was the second of two editions of the tournament in the 2021 tennis season. Mackenzie McDonald was the defending champion but lost in the second round to Tomáš Macháč.
Macháč won the title after defeating Sebastian Ofner 4–6, 6–4, 6–4 in the final.

## Seeds

* Kwon Soon-woo (quarterfinals)
* Emil Ruusuvuori (first round)
* Mikhail Kukushkin (first round)
* James Duckworth (quarterfinals)
* Taro Daniel (semifinals)
* Evgeny Donskoy (first round)
* Henri Laaksonen (first round)
* Prajnesh Gunneswaran (semifinals)

## 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 |
| | Tomáš Macháč | 6 | 1 | 6 | | | | |
| 8 | Prajnesh Gunneswaran | 3 | 6 | 2 | | | | |
| 8 | Prajnesh Gunneswaran | 3 | 6 | 2 | Tomáš Macháč | 4 | 6 | 6 |
| | | | | | Sebastian Ofner | 6 | 4 | 4 |
| | Sebastian Ofner | 6 | 6 | | Sebastian Ofner | 6 | 4 | 4 |
| 5 | Taro Daniel | 3 | 4 | | | | | |

### 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 | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 1 | S-w Kwon | 7 | 6 | | | | | | | | | | | | | | | | |
| | B Rola | 5 | 2 | | 1 | S-w Kwon | 7$^9$ | 6 | | | | | | | | | | | |
| | P Polansky | 7$^7$ | 4 | | | P Polansky | 6$^7$ | 4 | | | | | | | | | | | |
| LL | U Blanch | 6$^2$ | 3$^r$ | | | | | | | 1 | S-w Kwon | 2 | 1 | | | | | | |
| | M McDonald | 6 | 4 | 6 | | | | | | | T Macháč | 6 | 6 | | | | | | |
| | B Schnur | 3 | 6 | 4 | | M McDonald | 4 | 1 | | | | | | | | | | | |
| | T Macháč | 7 | 6 | | | T Macháč | 6 | 6 | | | | | | | | | | | |
| 7 | H Laaksonen | 5 | 2 | | | | | | | | | | | | | T Macháč | 6 | 1 | 6 |
| 4 | J Duckworth | 6 | 5 | 7 | | | | | | | | | | | 8 | P Gunneswaran | 3 | 6 | 2 |
| Q | A Kachmazov | 4 | 7 | 5 | 4 | J Duckworth | 6 | 6$^5$ | 7 | | | | | | | | | | |
| WC | A Nedovyesov | 5 | 3 | | Q | V Manafov | 2 | 7$^7$ | 5 | | | | | | | | | | |
| Q | V Manafov | 7 | 6 | | | | | | | 4 | J Duckworth | 4 | 6 | 6$^1$ | | | | | |
| WC | D Yevseyev | 4 | 6 | 3 | | | | | | 8 | P Gunneswaran | 6 | 2 | 7$^7$ | | | | | |
| | T Ito | 6 | 2 | 6 | | T Ito | 3 | 0$^r$ | | | | | | | | | | | |
| LL | J Lenz | 6 | 2 | 3 | 8 | P Gunneswaran | 6 | 2 | | | | | | | | | | | |
| 8 | P Gunneswaran | 3 | 6 | 6 | | | | | | | | | | | | | | | |

### Bottom half

| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 6 | E Donskoy | 2 | 4 | | | | | | | | | | | | | | |
| | S Ofner | 6 | 6 | | | S Ofner | 6 | 7$^7$ | | | | | | | | | |
| | D Popko | 4 | 4 | | WC | T Skatov | 3 | 6$^4$ | | | | | | | | | |
| WC | T Skatov | 6 | 6 | | | | | | | S Ofner | 7$^7$ | 4 | 7 | | | | |
| | R Ramanathan | 6 | 3 | 6 | | | | | | F Ferreira Silva | 6$^2$ | 6 | 5 | | | | |
| | H Grenier | 4 | 6 | 3 | | R Ramanathan | 4 | 5 | | | | | | | | | |
| | F Ferreira Silva | 6 | 7 | | | F Ferreira Silva | 6 | 7 | | | | | | | | | |
| 3 | M Kukushkin | 3 | 5 | | | | | | | | | | | | S Ofner | 6 | 6 |
| 5 | T Daniel | 6 | 6 | | | | | | | | | | | 5 | T Daniel | 3 | 4 |
| Q | R Peniston | 2 | 4 | | 5 | T Daniel | 6 | 6 | | | | | | | | | |
| | A Müller | 3 | 1$^r$ | | | D Istomin | 2 | 4 | | | | | | | | | |
| | D Istomin | 6 | 3 | | | | | | 5 | T Daniel | 6 | 6 | | | | | |
| Q | T-l Wu | 6 | 4 | 7$^7$ | | | | | Q | T-l Wu | 2 | 1 | | | | | |
| | M Kližan | 3 | 6 | 6$^5$ | Q | T-l Wu | 6 | 7$^{10}$ | | | | | | | | | |
| | V Troicki | 6 | 6 | | | V Troicki | 3 | 6$^8$ | | | | | | | | | |
| 2 | E Ruusuvuori | 4 | 2 | | | | | | | | | | | | | | |