Bellis, 15, who made a big splash at last year’s U.S. Open, advanced Friday to a potential third-round match against Williams by beating Zarina Diyas 6-2, 6-1 at the Miami Open in Key Biscayne, Fla. Williams was scheduled to play a second-round match Friday night against Monica Niculescu. Bellis was already relishing the chance to take on the owner of 19 Grand Slam titles. Bellis became the youngest player to win a match at the U.S.