Learner Tien has cruised to the quarterfinals of the men's singles tournament at the National Bank Open presented by Rogers.
The 20-year-old American beat Argentina's Thiago Agustin Tirante 6-4, 6-4 on Sunday afternoon at IGA Stadium.
Tirante had seven aces to Tien's two in the Round of 16 match.
Tien won 4 of 12 break points to Tirante's 2 of 10, however.
Defending champion Ben Shelton plays Joao Fonseca in one of the featured evening matches.
The fifth-seeded Shelton is the highest-ranked player left in the men's bracket.
Earlier on Sunday, Spain's Daniel Merida Aguilar defeated Tallon Griekspoor of the Netherlands 6-3, 6-1.
