# 2021 Croatia Open Umag – Singles

Carlos Alcaraz defeated Richard Gasquet in the final, 6–2, 6–2 to win the singles tennis title at the 2021 Croatia Open. It was his first ATP Tour title. With the victory, Alcaraz became the youngest player to win an ATP Tour title since Kei Nishikori at the 2008 Delray Beach International Tennis Championships.
Dušan Lajović was the reigning champion from when the tournament was last held in 2019, but lost to Daniel Altmaier in the quarterfinals.

## Seeds

The top four seeds receive a bye into the second round.
* Albert Ramos Viñolas (semifinals)
* Dušan Lajović (quarterfinals)
* Filip Krajinović (quarterfinals)
* Richard Gasquet (final)
* Aljaž Bedene (first round)
* Jaume Munar (first round)
* Carlos Alcaraz (champion)
* Gianluca Mager (second 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 | Semifinals | Final | Final | Final | Final |
| 1 | Albert Ramos Viñolas | 2 | 6$^3$ | | | | | |
| 7 | Carlos Alcaraz | 6 | 7$^7$ | | | | | |
| 7 | Carlos Alcaraz | 6 | 7$^7$ | | 7 | Carlos Alcaraz | 6 | 6 |
| | | | | | 4 | Richard Gasquet | 2 | 2 |
| 4 | Richard Gasquet | 7$^7$ | 3 | 6 | 4 | Richard Gasquet | 2 | 2 |
| Q | Daniel Altmaier | 6$^2$ | 6 | 3 | | | | |

### 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 | A Ramos Viñolas | 7 | 6 | | | | | | | | | |
| Q | A Collarini | 3 | 2 | | WC | D Ajduković | 5 | 4 | | | | | | | | | |
| WC | D Ajduković | 6 | 6 | | | | | | 1 | A Ramos Viñolas | 6 | 6 | | | | | |
| | C Taberner | 6 | 6 | | | | | | | S Travaglia | 2 | 1 | | | | | |
| WC | N Serdarušić | 2 | 2 | | | C Taberner | 4 | 3 | | | | | | | | | |
| | S Travaglia | 6 | 7$^7$ | | | S Travaglia | 6 | 6 | | | | | | | | | |
| 6 | J Munar | 3 | 6$^1$ | | | | | | | | | | | 1 | A Ramos Viñolas | 2 | 6$^3$ |
| | | | | | | | | | | | | | | 7 | C Alcaraz | 6 | 7$^7$ |
| | | | | | 3 | F Krajinović | 6 | 6 | | | | | | | | | |
| WC | H Rune | 6 | 3 | 2 | | R Albot | 4 | 2 | | | | | | | | | |
| | R Albot | 1 | 6 | 6 | | | | | 3 | F Krajinović | 6$^3$ | 6 | 1 | | | | |
| LL | R Olivo | 6 | 2 | 6$^1$ | | | | | 7 | C Alcaraz | 7$^7$ | 2 | 6 | | | | |
| | A Martin | 1 | 6 | 7$^7$ | | A Martin | 3 | 1 | | | | | | | | | |
| | L Pouille | 6 | 2 | 2 | 7 | C Alcaraz | 6 | 6 | | | | | | | | | |
| 7 | C Alcaraz | 3 | 6 | 6 | | | | | | | | | | | | | |

### 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 | Semifinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 5 | A Bedene | 1 | 4 | | | | | | | | | | | | | | | |
| | M Cecchinato | 6 | 6 | | | M Cecchinato | 3 | 1 | | | | | | | | | | |
| | D Džumhur | 6 | 6 | | | D Džumhur | 6 | 6 | | | | | | | | | | |
| Q | F Horanský | 4 | 3 | | | | | | | | D Džumhur | 3 | 6$^7$ | | | | | |
| Q | A Giannessi | 7$^7$ | 7 | | | | | | | 4 | R Gasquet | 6 | 7$^9$ | | | | | |
| | J Veselý | 6$^4$ | 5 | | Q | A Giannessi | 6$^4$ | 4 | | | | | | | | | | |
| | | | | | 4 | R Gasquet | 7$^7$ | 6 | | | | | | | | | | |
| | | | | | | | | | | | | | | 4 | R Gasquet | 7$^7$ | 3 | 6 |
| 8 | G Mager | 0 | 6 | 6 | | | | | | | | | | Q | D Altmaier | 6$^2$ | 6 | 3 |
| | P Martínez | 6 | 3 | 3 | 8 | G Mager | 6 | 1 | 5 | | | | | | | | | |
| Q | D Altmaier | 5 | 6 | 0 | Q | D Altmaier | 4 | 6 | 7 | | | | | | | | | |
| | C Moutet | 7 | 1 | 0$^r$ | | | | | | Q | D Altmaier | 6 | 6 | | | | | |
| | B Zapata Miralles | 4 | 6 | 6 | | | | | | 2 | D Lajović | 2 | 4 | | | | | |
| | P Cuevas | 6 | 2 | 4 | | B Zapata Miralles | 5 | 4 | | | | | | | | | | |
| | | | | | 2 | D Lajović | 7 | 6 | | | | | | | | | | |

## Qualifying
### Seeds

* Daniel Altmaier (qualified)
* Nikola Milojević (qualifying competition)
* Blaž Rola (first round)
* Alessandro Giannessi (qualified)
* Filip Horanský (qualified)
* Renzo Olivo (qualifying competition, lucky loser)
* Thomas Fabbiano (first round)
* Daniel Masur (first round)

### Qualifiers

* Daniel Altmaier
* Filip Horanský
* Andrea Collarini
* Alessandro Giannessi

### Lucky loser

* Renzo Olivo

### Qualifying draw
#### First qualifier

| First round | First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 1 | Daniel Altmaier | 2 | 6 | 6 | | | | | |
| Alt | Flavio Cobolli | 6 | 3 | 1 | | | | | |
| Alt | Flavio Cobolli | 6 | 3 | 1 | 1 | Daniel Altmaier | 3 | 6 | 6 |
| | | | | | WC | Matija Pecotić | 6 | 4 | 3 |
| WC | Matija Pecotić | 7 | 6 | | WC | Matija Pecotić | 6 | 4 | 3 |
| 7 | Thomas Fabbiano | 5 | 2 | | | | | | |

#### Second qualifier

| First round | First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 2 | Nikola Milojević | 6 | 7 | | | | | |
| | Lukáš Rosol | 4 | 5 | | | | | |
| | Lukáš Rosol | 4 | 5 | | 2 | Nikola Milojević | 2 | 2 |
| | | | | | 5 | Filip Horanský | 6 | 6 |
| WC | Hamad Međedović | 4 | 7$^7$ | 1 | 5 | Filip Horanský | 6 | 6 |
| 5 | Filip Horanský | 6 | 6$^2$ | 6 | | | | |

#### Third qualifier

| First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 3 | Blaž Rola | 4 | 2 | | | | |
| | Vitaliy Sachko | 6 | 6 | | | | |
| | Vitaliy Sachko | 6 | 6 | Vitaliy Sachko | 7$^7$ | 2 | 4 |
| | | | | Andrea Collarini | 6$^4$ | 6 | 6 |
| | Andrea Collarini | 6 | 6 | Andrea Collarini | 6$^4$ | 6 | 6 |
| 8 | Daniel Masur | 1 | 1 | | | | |

#### Fourth qualifier

| First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 4 | Alessandro Giannessi | 6 | 7 | | | | |
| | Rudolf Molleker | 3 | 5 | | | | |
| | Rudolf Molleker | 3 | 5 | 4 | Alessandro Giannessi | 7$^7$ | 6 |
| | | | | 6 | Renzo Olivo | 6$^5$ | 1 |
| Alt | Nerman Fatić | 3 | 1 | 6 | Renzo Olivo | 6$^5$ | 1 |
| 6 | Renzo Olivo | 6 | 6 | | | | |