# 2021 Challenger de Buenos Aires – Singles

Sumit Nagal was the defending champion but chose not to defend his title.
Sebastián Báez won the title after defeating Thiago Monteiro 6–4, 6–0 in the final.

## Seeds

* Thiago Monteiro (final)
* Juan Manuel Cerúndolo (semifinals)
* Francisco Cerúndolo (semifinals)
* Juan Pablo Varillas (quarterfinals)
* Hugo Dellien (quarterfinals)
* Thiago Seyboth Wild (first round)
* Sebastián Báez (champion)
* Tomás Martín Etcheverry (quarterfinals)

## 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 |
| 1 | Thiago Monteiro | 6 | 2 | 6 | | | | |
| 3 | Francisco Cerúndolo | 1 | 6 | 3 | | | | |
| 3 | Francisco Cerúndolo | 1 | 6 | 3 | 1 | Thiago Monteiro | 4 | 0 |
| | | | | | 7 | Sebastián Báez | 6 | 6 |
| 7 | Sebastián Báez | 6 | 6 | | 7 | Sebastián Báez | 6 | 6 |
| 2 | Juan Manuel Cerúndolo | 1 | 2 | | | | | |

### 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 | T Monteiro | 7$^9$ | 3 | 6 | | | | | | | | | | | | | | | |
| | H Casanova | 6$^7$ | 6 | 2 | 1 | T Monteiro | 6 | 6 | | | | | | | | | | | |
| | N Kicker | 6 | 2 | 6 | | N Kicker | 2 | 3 | | | | | | | | | | | |
| | N Álvarez | 3 | 6 | 3 | | | | | | 1 | T Monteiro | 6 | 3 | 7 | | | | | |
| | TA Tirante | 4 | 0 | | | | | | | 8 | TM Etcheverry | 4 | 6 | 5 | | | | | |
| | R Olivo | 6 | 6 | | | R Olivo | 6 | 6$^1$ | 4 | | | | | | | | | | |
| Q | Ignacio Monzón | 0 | 3 | | 8 | TM Etcheverry | 3 | 7$^7$ | 6 | | | | | | | | | | |
| 8 | TM Etcheverry | 6 | 6 | | | | | | | | | | | | 1 | T Monteiro | 6 | 2 | 6 |
| 3 | F Cerúndolo | 4 | 6 | 6 | | | | | | | | | | | 3 | F Cerúndolo | 1 | 6 | 3 |
| | C Ugo Carabelli | 6 | 1 | 4 | 3 | F Cerúndolo | 7 | 6 | | | | | | | | | | | |
| | JP Ficovich | 7$^7$ | 7$^8$ | | | JP Ficovich | 5 | 2 | | | | | | | | | | | |
| | N Sánchez Izquierdo | 6$^1$ | 6$^6$ | | | | | | | 3 | F Cerúndolo | 6 | 6 | | | | | | |
| Q | M Cuevas | 2 | 6 | 6 | | | | | | Q | M Cuevas | 1 | 1 | | | | | | |
| Q | F Comesaña | 6 | 3 | 2 | Q | M Cuevas | 7$^7$ | 7 | | | | | | | | | | | |
| WC | M Navone | 3 | 6 | 6 | WC | M Navone | 6$^0$ | 5 | | | | | | | | | | | |
| 6 | T Seyboth Wild | 6 | 1 | 2 | | | | | | | | | | | | | | | |

### 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 |
| 7 | S Báez | 3 | 6 | 6 | | | | | | | | | | | | | | |
| | P Cachin | 6 | 2 | 3 | 7 | S Báez | 6 | 6 | | | | | | | | | | |
| Q | C Gómez-Herrera | 3 | 4 | | | JI Londero | 3 | 4 | | | | | | | | | | |
| | JI Londero | 6 | 6 | | | | | | | 7 | S Báez | 7 | 6 | | | | | |
| | S Rodríguez Taverna | 6 | 1 | | | | | | | 4 | JP Varillas | 5 | 2 | | | | | |
| WC | RA Burruchaga | 4 | 4$^r$ | | | S Rodríguez Taverna | 4 | 2 | | | | | | | | | | |
| | N Hardt | 3 | 6 | 2 | 4 | JP Varillas | 6 | 6 | | | | | | | | | | |
| 4 | JP Varillas | 6 | 3 | 6 | | | | | | | | | | | 7 | S Báez | 6 | 6 |
| 5 | H Dellien | 4 | 6 | 6 | | | | | | | | | | | 2 | JM Cerúndolo | 1 | 2 |
| | F Díaz Acosta | 6 | 0 | 1 | 5 | H Dellien | 3 | 7 | 7$^8$ | | | | | | | | | |
| WC | JB Torres | 2 | 4 | | | F Meligeni Alves | 6 | 5 | 6$^6$ | | | | | | | | | |
| | F Meligeni Alves | 6 | 6 | | | | | | | 5 | H Dellien | 6 | 5 | 6$^5$ | | | | |
| | GA Olivieri | 2 | 6 | 5 | | | | | | 2 | JM Cerúndolo | 2 | 7 | 7$^7$ | | | | |
| | A Collarini | 6 | 4 | 7 | | A Collarini | 4 | 6 | 4 | | | | | | | | | |
| | G Andreozzi | 4 | 2 | | 2 | JM Cerúndolo | 6 | 3 | 6 | | | | | | | | | |
| 2 | JM Cerúndolo | 6 | 6 | | | | | | | | | | | | | | | |