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. Zverev advanced to face defending champion Alexei Popyrin of Australia in the quarterfinals.

Alexei Popyrin looped an unexpected backhand before raising his arms in stoic victory. The emotions of the moment were in stark contrast to what he felt just seconds earlier — and throughout a frustrating first set.