Roger Federer saved seven match points against unseeded Tennys Sandgren in an epic Australian Open quarter-final. Roger Federer defeated Tennys Sandgren of the United States 6-3, 2-6, 2-6, 7-6, 6-3 to advance to the Australian Open semi-finals. World number 100 Sandgren looked set to be the lowest-ranked player to reach the Melbourne semi-finals since 1991. But third seed Federer battled to win in three hours and 28 minutes. Federer will now face defending champion Novak Djokovic in the semi-final.