Melbourne - American No 1 and ninth seed John Isner was knocked out of the Australian Open on Monday in one of the biggest shocks of the first round.
The 6-foot-10 (2.08m) Isner was beaten by 6-foot-11 (2.11m) fellow American Reilly Opelka 7-6 (7/4), 7-6 (8/6), 6-7 (4/7), 7-6 (7/5) in a battle of the giants.
No fewer than 87 aces were powered down between the big-serving pair in what is the tallest match in Grand Slam history. There was just one break apiece registered in the fourth set of a match that lasted 2 hours and 58 minutes.
Isner, 33, had not lost a Grand Slam match to a player ranked as low as No 97 Opelka, who is 12 years his junior, since retiring due to a foot injury while trailing 106th-ranked Martin Klizan in the first round at Melbourne in 2014.
Opelka has never before reached the second round of a Grand Slam and will next face Italy's world No 102 Thomas Fabbiano, who beat Australian wildcard Jason Kubler 6-4, 7-6 (7/1), 2-6, 6-3.
Stefanos Tsitsipas (GRE x14) bt Matteo Berrettini (ITA) 6-7 (3/7), 6-4, 6-3, 7-6 (7/4)
Reilly Opelka (USA) bt John Isner (USA x9) 7-6 (7/4), 7-6 (8/6), 6-7 (4/7), 7-6 (7/5)
Yulia Putintseva (KAZ) bt Barbora Zahlavova Strycova (CZE x32) 6-4, 7-6 (7/1)
Lesya Tsurenko (UKR x24) bt Ekaterina Alexandrova (RUS) 6-4, 7-6 (7/4)