 Novak Djokovic shrugged off a slow start to power past unseated Australian Alexei Puprin, 4-6, 6-3, 6-4, 7-6, and into the Wimbledon fourth round on Saturday. His bid for a record-extending 25th Grand Slam title looked under threat when Puprin took a 4-3 lead with a blistering cross-court forehand winner and sealed the opening set with a second serve ace, but then he gathered himself and came back.