American teenager Learner Tien produced arguably the biggest shock of the Australian Open as he defeated last year’s runner-up Daniil Medvedev in five sets, 6-3, 7-6 (4), 6-7 (8), 1-6, 7-6 (7). The grueling, exhausting contest finished just before 3 a.m. in Melbourne and lasted four hours and 49 minutes, but it was the less experienced 19-year-old who prevailed in the final-set tiebreak to claim the biggest win of his fledgling career. Tien, who was making a first appearance in the second round of a grand slam, had an opportunity to close out the match in the third set before Medvedev launched an impressive comeback. But it was Tien who triumphed in the end. The teenager will now face world No. 69 Corentin Moutet in the third round. . . . #learnertien #medvedev #australianopen #tennis (📸 Paul Crock/AFP via Getty Images)