[gallery td_select_gallery_slide="slide" ids="29591,29590"] MELBOURNE — Novak Djokovic and Serena Williams reached the fourth round of the Australian Open without having lost a set between them Friday as the Grand Slam establishment held firm on day five of the championships. Tougher challenges will undoubtedly come but the untroubled progress of the two reigning champions and dominant players of 2015 has started to resemble a procession in the first week of the year's first Grand Slam. Djokovic, champion for five of the last eight years at Melbourne Park, played a rare match away from Rod Laver Arena but still proved too strong for Italian Andreas Seppi, securing his 210th Grand Slam victory 6-1, 7-5, 7-6(6). The Serbian had to work for his victory through some long rallies but always looked like he had an extra gear when he needed it. Serena did a twirl on Rod Laver Arena after crushing Russian teenager Daria Kasatkina 6-1, 6-1 to extend her record of wins to 71 matches, the post-match chatter quickly turning to her cropped-top outfit. "It's not warm but it's built for speed," the six-time champion quipped. Rain washed away much of the day's action on the outside courts at Melbourne Park, only intensifying the focus on the elite playing under cover on the three main arenas. Roger Federer is still very much part of that elite despite having gone three years without adding to his 17 Grand Slam titles and he notched up a record 300th Grand Slam victory for a man by beating Grigor Dimitrov 6-4, 3-6, 6-1, 6-4. Bulgarian Dimitrov was dubbed ‘Baby Fed' for his similarity in style to the Swiss master but after briefly troubling the four-time Australian Open champion to win the second set, he looked more pale imitation than doppelganger. When Federer was asked what he would write in a letter to his 18-year-old self, his answer might have been directed to Dimitrov and the others players trying to break into the top echelons of the game. "Talent takes you only so far. But the rest of it is you have to teach it to yourself and learn it, get it right," the 34-year-old said. "You got to be patient. Can't expect to win Slams at 16, 17, 18 any more these days, skyrocket through the rankings, unless you're out of this world." Fifth seed Maria Sharapova also lost a set to Lauren Davis but that only infuriated the 2008 champion and she raced through the decider 6-1, 6-7(5), 6-0 to claim her 600th WTA victory. The 28-year-old will next face Belinda Bencic, a teenager who is expected to be challenging for majors before too long. The Swiss was the first player into the round of 16 after overhauling Kateryna Bondarenko 4-6, 6-2, 6-4 and said she would not be intimidated by playing a five-time Grand Slam champion. Fourth seed Agnieszka Radwanska, a semifinalist in 2014, played through the pain of a leg injury to beat Puerto Rica's Monica Puig 6-4, 6-0. "Pain is my second name," the Pole said. "The spray doesn't work, the strapping doesn't work, I just have to get on with it." Radwanska next faces 21-year-old German Anna-Lena Friedsam, who beat last year's US Open runner up Roberta Vinci. Former US Open champion Marin Cilic was the one major casualty of the day in the men's draw, going down 6-4, 7-6(5), 7-5 to Roberto Bautista Agut. Japan's seventh seed Kei Nishikori brushed off a wrist problem to move past Guillermo Garcia-Lopez 7-5, 2-6, 6-3, 6-4 and set up a last 16 meeting with Jo-Wilfried Tsonga, who beat compatriot Pierre-Hugues Herbert 6-4, 7-6(7), 7-6(4). A night after Melbourne Park bid an emotional farewell to Lleyton Hewitt, the locals noisily embraced their newest darling after Daria Gavrilova backed up her upset of Petra Kvitova by beating Kristina Mladenovic 6-4, 4-6, 11-9. Hewitt was back on Rod Laver Arena to watch Australia's most promising young men's player, Nick Kyrgios, lose 6-3, 6-4, 1-6, 6-4 to sixth seed Tomas Berdych in typically tempestuous style.
