The United States’ Shelton has reached the last eight in Melbourne after Gaël Monfils’ unfortunate retirement in round four.

Ben Shelton ground down French veteran Gael Monfils Monday to set up an Australian Open quarter-final against Lorenzo Sonego, who ended teenage qualifier Learner Tien's fairytale run. But again nothing separated them until Shelton ended the resistance of Monfils with a series of winners to take the tiebreak and the veteran retired soon after.