Canadian Pospisil stuns Khachanov in first round

NEW YORK (Reuters) - Canada's Vasek Pospisil upset Russian ninth seed Karen Khachanov 4-6 7-5 7-5 4-6 6-3 on Tuesday to reach the second round of the U.S. Open.

Pospisil, who has fallen to 216th in the world rankings this year after having back surgery in January that sidelined him until Wimbledon, fired 15 aces and broke Khachanov four times during the nearly four-hour encounter.

The 29-year-old Canadian, who has never advanced past the second round in New York, will next face unseeded American Tennys Sandgren, who beat Frenchman Jo-Wilfried Tsonga.

(Reporting by Frank Pingue; Editing by Greg Stutchbury)