Novak Djokovic suffered his heaviest ever defeat in a three-set match on Friday when he was knocked out of the Vienna ATP tournament by lucky loser Lorenzo Sonego, stalling his bid to wrap up the year-end world number one ranking for a sixth time. Italian Sonego, ranked 42 and who had intially lost in qualifying last weekend, is the first lucky loser ever to beat Djokovic. His 6-2, 6-1 quarter-final stunner was 33-year-old Djokovic's heaviest ever defeat. The only other time the Serb had won just three games was at the 2005 Australian Open at the hands of Marat Safin in a best-of-five set encounter. "He just blew me off the court, that's all," Djokovic told atptour.com.

"He was better in every segment of the game. It was a pretty bad match from my side, but amazing from his side. "He definitely deserved this result," added the Serb star who was playing his first tournament since his Roland Garros final defeat to Rafal Nadal three weeks ago. Friday's defeat means Djokovic will have to wait a little longer before he completes the formality of equalling Pete Sampras's all-time record of ending the season top of the rankings for a sixth time.