Australian Open 2013: Andy Murray unsettled but reaches the fourth round in Melbourne But del Potro, known as the Tower of Tandil, was detonated yesterday by the unheralded Frenchman Jérémy Chardy. Meanwhile the 12th seed Marin Cilic - another potential quarter-final opponent - also lost to Italy's Andreas Seppi. The path to the last four has rarely featured so few high-ranked opponents. As for the two Frenchmen jousting for the chance to face Murray in Monday's fourth round, Gilles Simon and Gaël Monfils played each other almost to a standstill, with Simon finally coming through in five sets after more than four-and-a-half hours of combat. Simon had extensive massage on his serving arm during the later stages of a match which followed the rhythm of a waltz: slow, slow, quick, slow. One rally lasted 71 shots, and by the end of a match that finished at 12.40am, Simon was in so much agony his first-serve speed dropped below 70mph. "I was almost dying after the end of the second set, because we had already played two hours," said Simon afterwards. It [the pain] was everywhere, that was the problem. To have 60 seconds to work on it [at the changeovers] was not quite enough. I really need to recover before I think about playing Andy. Earlier, Murray had found the pocket-sized Berankis to be a surprisingly tenacious opponent. The Lithuanian is only 5ft 9in tall, which makes him an anomaly in a locker room full of beanpoles. Yet he is a former world junior No 1 who is on the books of the tennis super-agency IMG - all of which suggests that he must have a special gift. "He was making me feel pretty uncomfortable with his playing style," Murray said after the match. Indeed Berankis carved out no fewer than 12 break points, converting three of them to keep the crowd in suspense until the final shot. During one awkward moment in the second set, the courtside microphones picked Murray up muttering to himself about the standard of his recent practices. "I need to strike the ball better, my timing was off and in practice as well," he explained later, when TV interviewer Jim Courier asked him to elaborate. But while the Murray of a couple of years ago might have been disconcerted by such glitches, the new model knows that winning is what counts - and particularly winning in straight sets while your future opponents are slogging their way through ultra-marathons. His ever-pragmatic coach, Ivan Lendl, has helped him to let go of his more perfectionist tendencies. "Ivan knows that practice days are kind of irrelevant," Murray said last night. So long as you fire your body up and move your feet properly, it doesn't matter how you hit the ball. It's just good having someone like him to re-emphasise those points. In terms of the results, I'd rate my first week as nine of ten out of ten because I haven't had any long matches. Especially on the day when it was extremely hot, I was efficient in terms of the way I was playing. I'd like to play better, that's for sure. But it's also true that you don't want to play your best tennis in the first rounds of a tournament.