Top-seeded Alexander Zverev of Germany led Francisco Cerundolo 6-4, 1-0 when the 14th-seeded Argentine retired because of an abdominal injury Saturday night in the National Bank Open.

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.