MELBOURNE, Australia — Until he took on defending champion Novak Djokovic at Rod Laver Arena on opening Sunday in Australia, Dino Prizmic had never played a Grand Slam match. Frances Tiafoe, the 17th seed, beat Borna Coric 6-3, 7-6, 2-6, 6-3 in 3 1/2 hours and Daniel Elahi Galan needed almost five hours to beat Australia’s Jason Kubler 2-6, 6-3, …