American Alison Riske celebrates a hard-fought win against Australia's Casey Dellacqua to move into the quarter-finals. Picture: Getty Images

American Alison Riske celebrates a hard-fought win against Australia’s Casey Dellacqua to move into the quarter-finals. Picture: Getty Images

American Alison Riske celebrates a hard-fought win against Australia’s Casey Dellacqua to move into the quarter-finals. Picture: Getty Images