World No . 1 Novak Djokovic is on course for third successive Miami title . Serbian will next face 15th seed Tommy Haas in the last 16 of hard - court event . Maria Sharapova , three times a runner - up at Key Biscayne , also through to round four . Indian Wells winner will next play Czech world No . 22 Sandra Zakopalova .
World No . 1 Novak Djokovic stays on course for third successive Miami title . Serbian will next face 15th seed Tommy Haas in the last 16 of hard-court event . Maria Sharapova , four times a runner-up at Key Biscayne , also through to round four . Indian Wells winner will next play Czech world No . 22 Klara Zakopalova .