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.

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)

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