# 2021 Garden Open II – Singles

Andrea Pellegrino was the defending champion but lost in the quarterfinals to Flavio Cobolli.
Juan Manuel Cerúndolo won the title after defeating Cobolli 6–2, 3–6, 6–3 in the final.

## Seeds

* Damir Džumhur (first round)
* Hugo Dellien (first round)
* Federico Gaio (second round)
* Danilo Petrović (second round)
* Hugo Gaston (first round)
* Paolo Lorenzi (first round)
* Juan Pablo Varillas (first round)
* Alessandro Giannessi (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 | Final |
| | Cem İlkel | 3 | 5 | | | | | | |
| WC | Flavio Cobolli | 6 | 7 | | | | | | |
| WC | Flavio Cobolli | 6 | 7 | | WC | Flavio Cobolli | 2 | 6 | 3 |
| | | | | | | Juan Manuel Cerúndolo | 6 | 3 | 6 |
| 8 | Alessandro Giannessi | 6 | 4 | 5 | | Juan Manuel Cerúndolo | 6 | 3 | 6 |
| | Juan Manuel Cerúndolo | 4 | 6 | 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 |
| 1 | D Džumhur | 2 | 7$^7$ | 3 | | | | | | | | | | | | | | |
| Q | N Serdarušić | 6 | 6$^1$ | 6 | Q | N Serdarušić | 4 | 6 | 6 | | | | | | | | | |
| | A Vukic | 4 | 1 | | | R Marcora | 6 | 1 | 4 | | | | | | | | | |
| | R Marcora | 6 | 6 | | | | | | | Q | N Serdarušić | 6$^3$ | 6 | 3 | | | | |
| | D Masur | 6 | 4 | 6$^2$ | | | | | | | C İlkel | 7$^7$ | 3 | 6 | | | | |
| | C İlkel | 4 | 6 | 7$^7$ | | C İlkel | 6 | 6 | | | | | | | | | | |
| | L Giustino | 6 | 7 | | | L Giustino | 4 | 2 | | | | | | | | | | |
| 7 | JP Varillas | 1 | 5 | | | | | | | | | | | | | C İlkel | 3 | 5 |
| 4 | D Petrović | 6 | 7$^8$ | | | | | | | | | | | | WC | F Cobolli | 6 | 7 |
| Q | I Sijsling | 1 | 6$^6$ | | 4 | D Petrović | 2 | 2 | | | | | | | | | | |
| WC | F Cobolli | 6 | 6 | | WC | F Cobolli | 6 | 6 | | | | | | | | | | |
| | S Diez | 4 | 1 | | | | | | | WC | F Cobolli | 7$^7$ | 6 | | | | | |
| SE | A Pellegrino | 6 | 4 | 6 | | | | | | SE | A Pellegrino | 6$^3$ | 1 | | | | | |
| WC | S Napolitano | 4 | 6 | 4 | SE | A Pellegrino | 6 | 6$^4$ | 6 | | | | | | | | | |
| Alt | A Collarini | 6 | 6 | | Alt | A Collarini | 3 | 7$^7$ | 4 | | | | | | | | | |
| 5 | H Gaston | 1 | 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 | Semifinals |
| 8 | A Giannessi | 6 | 6 | | | | | | | | | | | | | | | | |
| | G Andreozzi | 3 | 3 | | 8 | A Giannessi | 6 | 6 | | | | | | | | | | | |
| | A Bolt | 0 | 3 | | | J Clarke | 2 | 4 | | | | | | | | | | | |
| | J Clarke | 6 | 6 | | | | | | | 8 | A Giannessi | 7 | 3 | 7 | | | | | |
| PR | T Kokkinakis | 6 | 6 | | | | | | | PR | T Kokkinakis | 5 | 6 | 5 | | | | | |
| | Y Maden | 3 | 2 | | PR | T Kokkinakis | 6$^8$ | 6 | 6 | | | | | | | | | | |
| | R Bemelmans | 6 | 3 | 2 | 3 | F Gaio | 7$^{10}$ | 3 | 4 | | | | | | | | | | |
| 3 | F Gaio | 3 | 6 | 6 | | | | | | | | | | | 8 | A Giannessi | 6 | 4 | 5 |
| 6 | P Lorenzi | 4 | 0 | | | | | | | | | | | | | JM Cerúndolo | 4 | 6 | 7 |
| | A Müller | 6 | 6 | | | A Müller | 4 | 3 | | | | | | | | | | | |
| | JM Cerúndolo | 7 | 7 | | | JM Cerúndolo | 6 | 6 | | | | | | | | | | | |
| Q | T Lamasine | 5 | 5 | | | | | | | | JM Cerúndolo | 6 | 6 | | | | | | |
| Q | F Meligeni Alves | 6 | 6 | | | | | | | WC | G Zeppieri | 0 | 3 | | | | | | |
| | E Couacaud | 3 | 4 | | Q | F Meligeni Alves | 4 | 3 | | | | | | | | | | | |
| WC | G Zeppieri | 1 | 6 | 6 | WC | G Zeppieri | 6 | 6 | | | | | | | | | | | |
| 2 | H Dellien | 6 | 3 | 4 | | | | | | | | | | | | | | | |