Coming off a season-opening triumph in Qatar, where he defeated his chief rival Andy Murray in the final, Novak Djokovic appeared to put his 2016 second-half slowdown behind him.
He entered the Australian Open as the No. 2 seed and two-time defending champion. Getting past the tough veteran Fernando Verdasco in straight sets in his opener was an encouraging sign, and helped firm up his status as a favorite for the title, which would be his seventh overall in Australia.
Denis Istomin had other plans.
Going into the match, Djokovic carried a perfect 5-0 record against his opponent and after taking a two-sets-to-one lead, it seemed like the sixth win was in sight.
Djokovic lost the fourth set in a tiebreaker, and then dropped the decider 6-4, marking his earliest loss at a major since Wimbledon in 2008. It was also his second time in three Grand Slams where he failed to reach at least the round of 16, having fallen to Sam Querrey in Wimbledon in 2016.
Credit to Istomin, who made it into the draw by earning a wildcard and ran all the way through to the fourth round.
