# 2021 San Diego Open – Singles

This was the first edition of the tournament, which was primarily organized to compensate for the cancellation of Asian tournaments in 2021 due to the COVID-19 pandemic.
Casper Ruud won the title, defeating Cameron Norrie in the final, 6–0, 6–2. It was Ruud's fifth victory of the season.

## Seeds

The top four seeds received a bye into the second round.
* Andrey Rublev (semifinals)
* Casper Ruud (champion)
* Félix Auger-Aliassime (withdrew)
* Denis Shapovalov (quarterfinals)
* Hubert Hurkacz (second round)
* Diego Schwartzman (quarterfinals)
* Cristian Garín (withdrew)
* Dan Evans (second round)
* Lorenzo Sonego (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 | Andrey Rublev | 6 | 3 | 4 | | | | |
| | Cameron Norrie | 3 | 6 | 6 | | | | |
| | Cameron Norrie | 3 | 6 | 6 | | Cameron Norrie | 0 | 2 |
| | | | | | 2 | Casper Ruud | 6 | 6 |
| | Grigor Dimitrov | 4 | 6 | 4 | 2 | Casper Ruud | 6 | 6 |
| 2 | Casper Ruud | 6 | 4 | 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 | Semifinals | Semifinals | Semifinals | Semifinals | Semifinals |
| | | | | | 1 | A Rublev | 6 | 6 | | | | | | | | | | |
| | F Fognini | 7$^7$ | 1 | 5 | WC | B Nakashima | 2 | 1 | | | | | | | | | | |
| WC | B Nakashima | 6$^5$ | 6 | 7 | | | | | | 1 | A Rublev | 6 | 7 | | | | | |
| | L Harris | 3 | 6 | 6 | | | | | | 6 | D Schwartzman | 1 | 5 | | | | | |
| Q | C Eubanks | 6 | 1 | 4 | | L Harris | 6 | 3 | 2 | | | | | | | | | |
| Q | F Gaio | 2 | 3 | | 6 | D Schwartzman | 4 | 6 | 6 | | | | | | | | | |
| 6 | D Schwartzman | 6 | 6 | | | | | | | | | | | 1 | A Rublev | 6 | 3 | 4 |
| | | | | | | | | | | | | | | | C Norrie | 3 | 6 | 6 |
| | | | | | 4 | D Shapovalov | 7$^9$ | 6 | | | | | | | | | | |
| Q | S Caruso | 4 | 6$^2$ | | | T Fritz | 6$^7$ | 2 | | | | | | | | | | |
| | T Fritz | 6 | 7$^7$ | | | | | | | 4 | D Shapovalov | 3 | 1 | | | | | |
| | D Koepfer | 2 | 5 | | | | | | | | C Norrie | 6 | 6 | | | | | |
| | C Norrie | 6 | 7 | | | C Norrie | 7$^7$ | 6 | | | | | | | | | | |
| LL | K Anderson | 6$^{11}$ | 5 | | 8 | D Evans | 6$^3$ | 3 | | | | | | | | | | |
| 8 | D Evans | 7$^{13}$ | 7 | | | | | | | | | | | | | | | |

### 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 |
| 5 | H Hurkacz | 7$^7$ | 6 | | | | | | | | | | | | | | | | |
| Q | A Bolt | 6$^2$ | 1 | | 5 | H Hurkacz | 7 | 4 | 2 | | | | | | | | | | |
| | A Karatsev | 6 | 7 | | | A Karatsev | 5 | 6 | 6 | | | | | | | | | | |
| | F Delbonis | 1 | 5 | | | | | | | | A Karatsev | 1 | 6 | 2 | | | | | |
| | M Fucsovics | 3 | 6 | 5 | | | | | | | G Dimitrov | 6 | 1 | 6 | | | | | |
| | G Dimitrov | 6 | 1 | 7 | | G Dimitrov | 6 | 6 | | | | | | | | | | | |
| | | | | | LL | A Holmgren | 1 | 1 | | | | | | | | | | | |
| | | | | | | | | | | | | | | | | G Dimitrov | 4 | 6 | 4 |
| 9 | L Sonego | 6 | 6 | | | | | | | | | | | | 2 | C Ruud | 6 | 4 | 6 |
| | N Basilashvili | 3 | 4 | | 9 | L Sonego | 6 | 6 | | | | | | | | | | | |
| | S Korda | 6 | 5 | 6 | | S Korda | 4 | 3 | | | | | | | | | | | |
| | T Paul | 3 | 7 | 1 | | | | | | 9 | L Sonego | 1 | 4 | | | | | | |
| LL | D Kudla | 3 | 2 | | | | | | | 2 | C Ruud | 6 | 6 | | | | | | |
| WC | A Murray | 6 | 6 | | WC | A Murray | 5 | 4 | | | | | | | | | | | |
| | | | | | 2 | C Ruud | 7 | 6 | | | | | | | | | | | |

## Qualifying
### Seeds

* Dominik Koepfer (moved to main draw)
* Kevin Anderson (qualifying competition, lucky loser)
* Jordan Thompson (first round)
* Steve Johnson (first round)
* Denis Kudla (qualifying competition, lucky loser)
* Salvatore Caruso (qualified)
* Alex Bolt (qualified)
* Mitchell Krueger (first round)

### Qualifiers

* Christopher Eubanks
* Alex Bolt
* Salvatore Caruso
* Federico Gaio

### Lucky losers

* Kevin Anderson
* Denis Kudla
* August Holmgren

### Qualifying draw
#### First qualifier

| First round | First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition |
| Alt | Lucas Gómez | 2 | 6 | 1 | | | |
| | Darian King | 6 | 3 | 6 | | | |
| | Darian King | 6 | 3 | 6 | Darian King | 6$^1$ | 5 |
| | | | | | Christopher Eubanks | 7$^7$ | 7 |
| | Christopher Eubanks | 6 | 3 | 6 | Christopher Eubanks | 7$^7$ | 7 |
| 8 | Mitchell Krueger | 1 | 6 | 3 | | | |

#### Second qualifier

| First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 2 | Kevin Anderson | 6 | 7 | | | | | |
| | Jason Kubler | 3 | 5 | | | | | |
| | Jason Kubler | 3 | 5 | 2 | Kevin Anderson | 7$^7$ | 3 | 5 |
| | | | | 7 | Alex Bolt | 6$^5$ | 6 | 7 |
| WC | Alafia Ayeni | 4 | 6$^5$ | 7 | Alex Bolt | 6$^5$ | 6 | 7 |
| 7 | Alex Bolt | 6 | 7$^7$ | | | | | |

#### Third qualifier

| First round | First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 3 | Jordan Thompson | 4 | 6$^6$ | | | | | | |
| Alt | August Holmgren | 6 | 7$^8$ | | | | | | |
| Alt | August Holmgren | 6 | 7$^8$ | | Alt | August Holmgren | 6 | 3 | 6$^7$ |
| | | | | | 6 | Salvatore Caruso | 4 | 6 | 7$^9$ |
| | Ernesto Escobedo | 5 | 6 | 4 | 6 | Salvatore Caruso | 4 | 6 | 7$^9$ |
| 6 | Salvatore Caruso | 7 | 1 | 6 | | | | | |

#### Fourth qualifier

| First round | First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 4 | Steve Johnson | 6 | 6$^4$ | 3 | | | | |
| | Federico Gaio | 3 | 7$^7$ | 6 | | | | |
| | Federico Gaio | 3 | 7$^7$ | 6 | | Federico Gaio | 6 | 6 |
| | | | | | 5 | Denis Kudla | 4 | 2 |
| WC | Zachary Svajda | 6 | 2 | 4 | 5 | Denis Kudla | 4 | 2 |
| 5 | Denis Kudla | 3 | 6 | 6 | | | | |