Kazakhstan's Elena Rybakina advanced to the National Bank Open semifinals after Ukraine's Marta Kostyuk was forced to retire with an apparent arm injury while trailing 6-1, 2-1 in women's singles action Monday in Montreal.

Alexander Zverev fired a ball into the hazy, evening sky — and right out of Sobeys Stadium in frustration. A few years back, the damage might have been a lot worse. The National Bank Open favourite had just lost the tiebreak in a knife-edged first set off a shot that clipped the net with a semifinal berth on the line.

Defending champion Alexei Popyrin of Australia beat fifth-seeded Holger Rune of Denmark 4-6, 6-2, 6-3 on Saturday night to reach the National Bank Open quarterfinals.