WATCH: Denis Istomin sends Novak Djokovic home early in Melbourne

Calling the match for ESPN, John McEnroe proclaimed that we might have just witnessed the biggest upset of the past decade.

That’s up for debate, but what isn’t in question is that nobody could have possibly predicted that world No. 117 Denis Istomin would beat six-time champion Novak Djokovic in the second round of the Australian Open on Thursday.

As unfathomable as it may seem, that’s exactly what the 30-year-old journeyman pulled off. The Uzbekistani, who had taken just one set off Djokovic in five previous matches against him, played brilliantly in a 7-6 (8), 5-7, 2-6, 7-6 (5), 6-4 triumph that lasted just under five hours.

This match was a marathon in every sense of the word. The first game took 16 minutes to complete, and the first set wrapped up after 87 minutes of play. It was such a dogfight that the two competitors joked during a changeover that they should simply skip the set and go straight to a tiebreaker.

As it would happen, the first set would ultimately be decided by a tiebreak, with Istomin narrowly taking it. In the second set, the underdog failed to convert two sets points, and the world No. 2 took advantage to level the match.

That, at the time, seemed like the turning point in the contest. After wasting such a golden opportunity, would the wild card have the mental strength to regroup and rebound? The prospect of an upset got even slimmer when Djokovic won the third set by a commanding 6-2 score.

In the fourth, Istomin won his second tiebreak of the match, on the fourth set point, sending this one, almost improbably, into a decider.

Clearly running on adrenaline, with the crowd support behind him, Istomin went up a break, 3-2, and held his ground to finish Djokovic and send the six-time Australian Open champion home early.

Can Istomin, who has a losing record for his career and just one title in nine years on tour, build off the most significant victory of his life? We’ll find out on Saturday when he takes on 30th seed Pablo Carreño Busta in the third round.