2021 San Diego Open

Singles Casper Ruud defeated Cameron Norrie, 6–0, 6–2 • It was Ruud's 5th and last singles title of the year and the 6th of his career. Doubles Joe Salisbury / Neal Skupski defeated John Peers / Filip Polášek, 7–6(7–2), 3–6, [10–5] ==Singles main-draw entrants==

Seeds • 1 Rankings are as of 20 September 2021. Other entrants The following players received wildcards into the main draw: • Andy Murray • Brandon Nakashima • Kei Nishikori The following player received entry as a special exempt: • Kwon Soon-woo The following players received entry from the qualifying draw: • Alex Bolt • Salvatore Caruso • Christopher Eubanks • Federico Gaio The following players received entry as lucky losers: • Kevin Anderson • August Holmgren • Denis Kudla Withdrawals ;Before the tournament • Félix Auger-Aliassime → replaced by August Holmgren • Cristian Garín → replaced by Dominik Koepfer • David Goffin → replaced by Sebastian Korda • Kwon Soon-woo → replaced by Kevin Anderson • Dušan Lajović → replaced by Lloyd Harris • Kei Nishikori → replaced by Denis Kudla • Reilly Opelka → replaced by Federico Delbonis ==Doubles main-draw entrants==

Seeds • 1 Rankings are as of 20 September 2021. Other entrants The following pairs received wildcards into the doubles main draw: • Brandon Nakashima / Sem Verbeek • Antonio Šančić / Artem Sitak Withdrawals ;Before the tournament • Nicholas Monroe / Frances Tiafoe → replaced by Dominik Koepfer / Nicholas Monroe • Rajeev Ram / Jack Sock → replaced by Jordan Thompson / Jackson Withrow ==References==