# 2021 Sparkassen ATP Challenger – Singles

Ilya Ivashka was the defending champion but chose not to defend his title.
Oscar Otte won the title after defeating Maxime Cressy 7–6$^{(7–5)}$, 6–4 in the final.

## Seeds

* Oscar Otte (champion)
* Maxime Cressy (final)
* Quentin Halys (second round)
* Emilio Gómez (first round)
* Federico Gaio (quarterfinals)
* Fernando Verdasco (first round)
* Marc-Andrea Hüsler (second round)
* Alessandro Giannessi (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 |
| 1 | Oscar Otte | 7$^7$ | 6 | | | | |
| | Jack Draper | 6$^3$ | 4 | | | | |
| | Jack Draper | 6$^3$ | 4 | 1 | Oscar Otte | 7$^7$ | 6 |
| | | | | 2 | Maxime Cressy | 6$^5$ | 4 |
| | Mirza Bašić | 5 | 2 | 2 | Maxime Cressy | 6$^5$ | 4 |
| 2 | Maxime Cressy | 7 | 6 | | | | |

### Top 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 |
| 1 | O Otte | 7$^7$ | 7$^7$ | | | | | | | | | | | | | | |
| | R Marcora | 6$^1$ | 6$^4$ | | 1 | O Otte | 6 | 6 | | | | | | | | | |
| | M Bachinger | 6 | 6$^9$ | 7$^8$ | | M Bachinger | 3 | 1 | | | | | | | | | |
| Q | Tobias Simon | 3 | 7$^{11}$ | 6$^6$ | | | | | 1 | O Otte | 6 | 6 | | | | | |
| | R Peniston | 6 | 6 | | | | | | | R Peniston | 2 | 4 | | | | | |
| Q | A Cozbinov | 3 | 2 | | | R Peniston | 7$^7$ | 6 | | | | | | | | | |
| | GM Moroni | 4 | 6$^1$ | | 7 | M-A Hüsler | 6$^1$ | 4 | | | | | | | | | |
| 7 | M-A Hüsler | 6 | 7$^7$ | | | | | | | | | | | 1 | O Otte | 7$^7$ | 6 |
| 4 | E Gómez | 4 | 2 | | | | | | | | | | | | J Draper | 6$^3$ | 4 |
| | J Draper | 6 | 6 | | | J Draper | 6 | 7$^7$ | | | | | | | | | |
| WC | M Arnaldi | 6$^9$ | 0 | | Q | L Miedler | 4 | 6$^1$ | | | | | | | | | |
| Q | L Miedler | 7$^{11}$ | 6 | | | | | | | J Draper | 6$^6$ | 7$^7$ | 6 | | | | |
| | D Stricker | 6 | 3 | 7 | | | | | 5 | F Gaio | 7$^8$ | 6$^5$ | 2 | | | | |
| | M Viola | 4 | 6 | 5 | | D Stricker | 6$^5$ | 6$^2$ | | | | | | | | | |
| | N Kuhn | 3 | 6$^5$ | | 5 | F Gaio | 7$^7$ | 7$^7$ | | | | | | | | | |
| 5 | F Gaio | 6 | 7$^7$ | | | | | | | | | | | | | | |

### 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 | F Verdasco | 6$^6$ | 6 | 3 | | | | | | | | | | | | | |
| | V Sachko | 7$^8$ | 4 | 6 | | V Sachko | 6 | 6 | | | | | | | | | |
| | B Gojo | 6 | 7$^7$ | | | B Gojo | 2 | 4 | | | | | | | | | |
| | D Masur | 4 | 6$^4$ | | | | | | | V Sachko | 6$^3$ | 6 | 2 | | | | |
| | M Bašić | 6 | 6 | | | | | | | M Bašić | 7$^7$ | 3 | 6 | | | | |
| | E Karlovskiy | 4 | 3 | | | M Bašić | 7$^{14}$ | 6 | | | | | | | | | |
| WC | L Nardi | 4 | 3 | | 3 | Q Halys | 6$^{12}$ | 3 | | | | | | | | | |
| 3 | Q Halys | 6 | 6 | | | | | | | | | | | | M Bašić | 5 | 2 |
| 8 | A Giannessi | 7$^8$ | 3 | 5 | | | | | | | | | | 2 | M Cressy | 7 | 6 |
| Q | N Fatić | 6$^6$ | 6 | 7 | Q | N Fatić | 6$^1$ | 2 | | | | | | | | | |
| | M Copil | 6 | 7$^7$ | | | M Copil | 7$^7$ | 6 | | | | | | | | | |
| WC | Alexander Weis | 4 | 6$^5$ | | | | | | | M Copil | 6$^8$ | 4 | | | | | |
| | C-h Tseng | 6 | 3 | 4 | | | | | 2 | M Cressy | 7$^{10}$ | 6 | | | | | |
| | R Quiroz | 4 | 6 | 6 | | R Quiroz | 6$^3$ | 4 | | | | | | | | | |
| | T van Rijthoven | 6$^6$ | 5 | | 2 | M Cressy | 7$^7$ | 6 | | | | | | | | | |
| 2 | M Cressy | 7$^8$ | 7 | | | | | | | | | | | | | | |