Australian Open 2017: Andy Murray, Roger Federer face stern tests; Angelique Kerber targets last 16

Melbourne: Andy Murray will hope to avoid following title-holder Novak Djokovic out of the Australian Open on Friday when he plays Sam Querrey, who has giant-killing form at Grand Slam level. Murray will have been an interested observer as Djokovic, who has beaten him in four finals at Melbourne Park, suffered a huge upset against the unheralded Denis Istomin on Thursday. [caption id=“attachment_3212154” align=“alignleft” width=“380”]  ]Andy Murray hits a shot during the second round match at the Australian Open. Reuters[/caption] But the world number one now faces Querrey, who stunned Djokovic at this stage, the third round, at Wimbledon last year, a defeat that heralded the Serb’s downward spiral. Querrey, 29, has never gone beyond the third round and he has only beaten Murray once in seven attempts. But he will take heart from last year’s run to the Wimbledon quarter-finals. Another possible concern for Murray against the American, ranked 32, is the state of his right ankle, which he rolled painfully during his second-round win over Andrey Rublev. “Heard a few sort of little crackles, and it was sore. It was throbbing kind of the rest of the match. I was moving fine on it, though. It was just sore,” he said. However, Murray was back in training on Thursday, the day after his match with Rublev, and he has given assurances that he has no major problems. Elsewhere Roger Federer faces a major hurdle when he takes on world number 10 Tomas Berdych, an old rival who took him to five sets in Melbourne in 2009. Federer, seeded 17th after a long injury break last year, leads their head-to-head 16-6 and he has won all three of his Australian Open matches against the Czech. “I know I’ve got to lift my game a little bit,” admitted the 17-time Grand Slam champion, now 35. “He’s caused difficulties for me in the past on faster courts… I know what he’s got. I don’t need to tell you where he’s beaten me. “Then again, I’ve played him here, played him on many occasions, as well, when it went my way. I’ve just got to play on my terms and really be focused on my own service games to make sure I don’t have any lapses there.” In the women’s draw, defending champion Angelique Kerber will expect to sail into the fourth round when she plays Kristyna Pliskova, twin sister of US Open finalist Karolina. And Venus Williams goes into a first career meeting with China’s Duan Yingying, who says she has never even seen the seven-time Grand Slam-winner play.