# 2021 Split Open – Singles

Francisco Cerúndolo was the defending champion but chose not to defend his title.
Blaž Rola won the title after defeating Blaž Kavčič 2–6, 6–3, 6–2 in the final.

## Seeds

* Pedro Sousa (first round, retired)
* Marc Polmans (first round)
* Sebastian Ofner (first round)
* Mohamed Safwat (first round)
* Danilo Petrović (quarterfinals)
* Blaž Rola (champion)
* Kimmer Coppejans (second round)
* Filip Horanský (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 | Semifinals | Final | Final | Final | Final | Final |
| Alt | Kacper Żuk | 6 | 3 | 2 | | | | | |
| Q | Blaž Kavčič | 2 | 6 | 6 | | | | | |
| Q | Blaž Kavčič | 2 | 6 | 6 | Q | Blaž Kavčič | 6 | 3 | 2 |
| | | | | | 6 | Blaž Rola | 2 | 6 | 6 |
| | Andrea Collarini | 6$^3$ | 7$^7$ | 4 | 6 | Blaž Rola | 2 | 6 | 6 |
| 6 | Blaž Rola | 7$^7$ | 6$^3$ | 6 | | | | | |

### 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 | P Sousa | 2$^r$ | | | | | | | | | | | | | | | | | |
| Alt | K Żuk | 1 | | | Alt | K Żuk | 6 | 6 | | | | | | | | | | | |
| | J Clarke | 6$^1$ | 0 | | WC | N Serdarušić | 4 | 2 | | | | | | | | | | | |
| WC | N Serdarušić | 7$^7$ | 6 | | | | | | | Alt | K Żuk | 7$^8$ | 6 | | | | | | |
| Q | A Santillan | 2 | 0$^r$ | | | | | | | PR | T Kokkinakis | 6$^6$ | 3 | | | | | | |
| SE | Z Kolář | 6 | 5 | | SE | Z Kolář | 6$^3$ | 1 | | | | | | | | | | | |
| PR | T Kokkinakis | 3 | 6 | 6 | PR | T Kokkinakis | 7$^7$ | 6 | | | | | | | | | | | |
| 8 | F Horanský | 6 | 4 | 4 | | | | | | | | | | | Alt | K Żuk | 6 | 3 | 2 |
| 4 | M Safwat | 3 | 3 | | | | | | | | | | | | Q | B Kavčič | 2 | 6 | 6 |
| Q | B Kavčič | 6 | 6 | | Q | B Kavčič | 4 | 7$^9$ | 6 | | | | | | | | | | |
| | E Ymer | 6 | 6 | | | E Ymer | 6 | 6$^7$ | 4 | | | | | | | | | | |
| | A Müller | 0 | 4 | | | | | | | Q | B Kavčič | 4 | 6 | 6 | | | | | |
| | A Vukic | 6 | 6 | | | | | | | | A Vukic | 6 | 2 | 2 | | | | | |
| WC | M Poljičak | 1 | 1 | | | A Vukic | 2 | 6 | 6 | | | | | | | | | | |
| | B Tomic | 2 | 6 | 3 | 7 | K Coppejans | 6 | 4 | 4 | | | | | | | | | | |
| 7 | K Coppejans | 6 | 4 | 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 | D Petrović | 6 | 6 | | | | | | | | | | | | | | | |
| | L Rosol | 1 | 3 | | 5 | D Petrović | 6 | 6 | | | | | | | | | | |
| | J Domingues | 5 | 3 | | | M Marterer | 1 | 3 | | | | | | | | | | |
| | M Marterer | 7 | 6 | | | | | | | 5 | D Petrović | 2 | 3 | | | | | |
| | A Bolt | 4 | 2 | | | | | | | | A Collarini | 6 | 6 | | | | | |
| Q | U Ignatik | 6 | 6 | | Q | U Ignatik | 6 | 2 | 1 | | | | | | | | | |
| | A Collarini | 6 | 6 | | | A Collarini | 2 | 6 | 6 | | | | | | | | | |
| 3 | S Ofner | 4 | 4 | | | | | | | | | | | | A Collarini | 6$^3$ | 7$^7$ | 4 |
| 6 | B Rola | 6 | 6 | | | | | | | | | | | 6 | B Rola | 7$^7$ | 6$^3$ | 6 |
| | D Popko | 3 | 4 | | 6 | B Rola | 6 | 7 | | | | | | | | | | |
| WC | D Ajduković | 2 | 6 | 7 | WC | D Ajduković | 1 | 5 | | | | | | | | | | |
| PR | D Brown | 6 | 4 | 5 | | | | | | 6 | B Rola | 6 | 6 | | | | | |
| Q | M Bašić | 7$^7$ | 6 | | | | | | | Q | M Bašić | 2 | 4 | | | | | |
| | C İlkel | 6$^4$ | 3 | | Q | M Bašić | 7$^7$ | 6 | | | | | | | | | | |
| | R Haase | 6 | 4 | 7$^7$ | | R Haase | 6$^4$ | 3 | | | | | | | | | | |
| 2 | M Polmans | 3 | 6 | 6$^4$ | | | | | | | | | | | | | | |