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.

Top-seeded Alexander Zverev advanced to an ATP Toronto Masters quarter-final against defending champion Alexei Popyrin as his fourth-round opponent Francisco Cerundolo was forced to retire with an ...