# 2021 JC Ferrero Challenger Open – Singles

Carlos Alcaraz was the defending champion but chose not to defend his title.
Constant Lestienne won the title after defeating Hugo Grenier 6–4, 6–3 in the final.

## Seeds

* Feliciano López (second round)
* Fernando Verdasco (second round)
* Oscar Otte (semifinals)
* Quentin Halys (first round)
* Dmitry Popko (first round)
* Kacper Żuk (second round)
* Mario Vilella Martínez (second round)
* João Sousa (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 |
| | Hugo Grenier | 6 | 6$^3$ | 6 | | | |
| 3 | Oscar Otte | 3 | 7$^7$ | 4 | | | |
| 3 | Oscar Otte | 3 | 7$^7$ | 4 | Hugo Grenier | 4 | 3 |
| | | | | | Constant Lestienne | 6 | 6 |
| 8 | João Sousa | 4 | 6$^5$ | | Constant Lestienne | 6 | 6 |
| | Constant Lestienne | 6 | 7$^7$ | | | | |

### 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/WC | F López | 6 | 6 | | | | | | | | | | | | | | | | |
| | R Marcora | 3 | 1 | | 1/WC | F López | 3 | 5 | | | | | | | | | | | |
| WC | Em Nava | 6$^3$ | 4 | | | H Grenier | 6 | 7 | | | | | | | | | | | |
| | H Grenier | 7$^7$ | 6 | | | | | | | | H Grenier | 6 | 3 | 6 | | | | | |
| | M Geerts | 3 | 7$^7$ | 1 | | | | | | | N Borges | 4 | 6 | 4 | | | | | |
| | N Borges | 6 | 6$^5$ | 6 | | N Borges | 3 | 6 | 6 | | | | | | | | | | |
| Q | Georgii Kravchenko | 3 | 2 | | 7 | M Vilella Martínez | 6 | 3 | 1 | | | | | | | | | | |
| 7 | M Vilella Martínez | 6 | 6 | | | | | | | | | | | | | H Grenier | 6 | 6$^3$ | 6 |
| 3 | O Otte | 6 | 6 | | | | | | | | | | | | 3 | O Otte | 3 | 7$^7$ | 4 |
| | A Menéndez Maceiras | 2 | 3 | | 3 | O Otte | 6 | 6 | | | | | | | | | | | |
| | T Fabbiano | 6 | 3 | 6 | | T Fabbiano | 1 | 4 | | | | | | | | | | | |
| | R Ramanathan | 4 | 6 | 3 | | | | | | 3 | O Otte | 7$^{10}$ | 6 | | | | | | |
| | K Jacquet | 2 | 6 | 2$^r$ | | | | | | Q | D Yevseyev | 6$^8$ | 1 | | | | | | |
| | D Istomin | 6 | 4 | 3 | | D Istomin | 5 | 4 | | | | | | | | | | | |
| Q | D Yevseyev | 7$^7$ | 6 | | Q | D Yevseyev | 7 | 6 | | | | | | | | | | | |
| 5 | D Popko | 6$^5$ | 4 | | | | | | | | | | | | | | | | |

### 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 | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 8 | J Sousa | 6 | 7$^7$ | | | | | | | | | | | | | | | |
| | M Viola | 1 | 6$^5$ | | 8 | J Sousa | 6 | 3 | 6 | | | | | | | | | |
| Q | S Balaji | 5 | 6 | 6 | Q | S Balaji | 2 | 6 | 4 | | | | | | | | | |
| WC | N Álvarez Varona | 7 | 4 | 4 | | | | | | 8 | J Sousa | 3 | 6 | 6 | | | | |
| Alt | V Orlov | 2 | 1 | | | | | | | | F Ferreira Silva | 6 | 3 | 4 | | | | |
| Alt | M Zverev | 6 | 6 | | Alt | M Zverev | 2 | 0 | | | | | | | | | | |
| | F Ferreira Silva | 6$^3$ | 7$^7$ | 7$^8$ | | F Ferreira Silva | 6 | 6 | | | | | | | | | | |
| 4 | Q Halys | 7$^7$ | 6$^4$ | 6$^6$ | | | | | | | | | | | 8 | J Sousa | 4 | 6$^5$ |
| 6 | K Żuk | 5 | 7$^7$ | 6 | | | | | | | | | | | | C Lestienne | 6 | 7$^7$ |
| | T Gabashvili | 7 | 6$^1$ | 3 | 6 | K Żuk | 5 | 3 | | | | | | | | | | |
| Q | S Rodríguez Taverna | 5 | 3 | | Alt | L Miedler | 7 | 6 | | | | | | | | | | |
| Alt | L Miedler | 7 | 6 | | | | | | | Alt | L Miedler | 6$^5$ | 4 | | | | | |
| | C Lestienne | 6 | 7 | | | | | | | | C Lestienne | 7$^7$ | 6 | | | | | |
| | B Gojo | 4 | 5 | | | C Lestienne | 5 | 7$^7$ | 7 | | | | | | | | | |
| | N Kuhn | 4 | 3 | | 2 | F Verdasco | 7 | 6$^4$ | 5 | | | | | | | | | |
| 2 | F Verdasco | 6 | 6 | | | | | | | | | | | | | | | |