Roger Federer the five-time champion has been knocked out of the US Open in the fourth round by unseeded world number 55 John Millman from Australia. Federer lost in four sets 3-6 7-5 7-6 7-6, after the match Millman said he felt a bit guilty beating his hero. Next up for Millman is Novak Djokovic in the last eight. Crowd favourite Juan Martin Del Potro overcame John Isner this evening to reach the semi-finals, former champion Del Potro winning the match 6-7 6-3 7-6 6-2 and will now face World number Rafael Nadal or Dominic Thiem on Friday.