Former world No.1 Venus Williams, idled for six months, upset Czech third seed Petra Kvitova 6-4 4-6 6-0 today to reach the third round of the US$9.6 million ($NZ 11.6) WTA and ATP Miami hardcourt event.
Seven-time grand slam champion Williams, in her first WTA event since pulling out of last year's US Open, took advantage on 9-of-11 break-point chances and fought off a rally to advance after two hours and 18 minutes.
Williams booked a third-round matchup with Canadian wildcard Aleksandra Wozniak, who defeated Romania's Monica Niculescu 4-6 6-3 6-4.
At last year's US Open, Williams withdrew after a first-round triumph and revealed she had been diagnosed with the auto-immune disorder Sjogren syndrome, an illness that saps her energy and causes pain in her joints.
She played doubles for the US Fed Cup team last month and defeated Japan's Kimiko Date-Krumm 6-0 6-3 in her WTA return match on Wednesday in round one.