It was only the second time in the Serb’s career that he has managed to win just three games in a match, the previous occasion coming against Marat Safin at the 2005 Australian Open.
To make the result all the more incredible, it is the first time in his career that Djokovic has lost to a lucky loser, a player given a place in the tournament’s main draw despite losing in qualifying.
Sonego, ranked No. 42 in the world, took just 68 minutes to dismantle Djokovic and inflict only his third defeat of the season.
Djokovic has already wrapped up the No. 1 year-end ranking for a sixth time, matching Pete Sampras’ all-time record, and claimed that it affected his performance.
Sonego will play either Bulgarian Grigor Dimitrov or Great Britain’s Dan Evans in the semifinal.
Next up for Djokovic is the prestigious ATP Finals, being held in London for the final time. There he will be aiming to win a sixth singles title, which would tie the record held by Roger Federer.