MELBOURNE :Defending champion Novak Djokovic survived a huge scare before beating home hope Alexei Popyrin 6-3 4-6 7-6(4) 6-3 to reach the third round of the Australian Open on Wednesday.The 36-year-old Serb, bidding for a record-extending 11th crown in Melbourne, was in deep trouble in the third set when errors began to flow and he had to save four set points.With the packed night-time crowd on the edge of their seats, top seed Djokovic used his vast experience to win the pivotal tiebreak and then broke a dispirited Popyrin midway through the fourth set to finally seize control.Djokovic breezed through the fourth set to rack up his 30th successive victory at the Australian Open - his last defeat coming in 2018 - but for the second successive round he was pushed hard and looked short of his best form."He missed an easy forehand and I was lucky to get away with that game," Djokovic, who was riled up by a heckling fan as the match neared its conclusion, said on court."He was the better player for a set and a half but the momentum shifted after the tiebreak."Djokovic, bidding to claim a record 25th Grand Slam title, was kept on court four hours during his opening round victory over Croatian qualifier Dino Prizmic on Sunday.But when he took the opening set against Popyrin in 39 minutes having lost only three points on serve, it seemed a more routine victory was on the cards.Djokovic had a 13-1 record against Australian players at Grand Slams but the 24-year-old Popyrin was not about to go down meekly as he fired up his serve and forehand to start denting the Serb's armour.The crowd burst into life when Djokovic faced a break point at 1-2 in the second set and Popyrin converted it with a deft volley.Popyrin wavered, however,