Oct 20 (OPTA) - Results from the ATP World Tour 250, Stockholm Men's Singles matches on Friday .. Quarter-final .. 1-John Isner (USA) beat Tennys Sandgren (USA) 7-6(8) 6-7(5) 7-6 Ernests Gulbis (LAT) beat 4-Jack Sock (USA) 4-6 6-3 6-4 3-Stefanos Tsitsipas (GRE) beat Philipp Kohlschreiber 6-3 7-6(4) (GER) 2-Fabio Fognini (ITA) beat 6-Hyeon Chung (KOR) 7-5 (Retired)