Eugenie Bouchard of Montreal eliminated Shahar Peer in straight sets on Tuesday night at the Mexico Open in Acapulco.
Bouchard won by scores of 6-2, 6-2 over the Israel native, who was once ranked 14th in the world but has slid to 85th.
Bouchard, ranked 19th in the world, later in the night tweeted a balloon-filled photo of thanks to fans who wished her well on her 20th birthday.
The second seed in the tournament, Bouchard on Wednesday faces Lara Arruabarrena of Spain.
Aleksandra Wozniak of Blainville, Que., also advanced, surviving Barty 7-6 (5), 5-7, 6-2 to set up a match with China's Shuai Zhang.
Sharon Fichman of Toronto also moved on, blasting fifth seed Yvonne Meusburger of Austria 6-1, 6-3.
Fichman next battles Caroline Garcia of France.
Top-seeded Dominika Cibulkova had a 6-3, 6-4 win over Urszula Radwanska, from Poland, American Victoria Duval had a 6-2, 6-4 win over Czech Iveta Melzer and Estonian Kai Kanepi prevailed 6-1, 3-6, 6-2 against Jana Cepelova, from Slovakia.
On the men's side of the combined ATP-WTA tournament, Alexandr Dolgopolov, from the Ukraine, beat Vasek Pospisil of Vancouver 6-2, 6-2
While he didn't win, Pospisil on Twitter said he was happy to be back in action after a back injury, which forced him to miss Davis Cup action for Canada last month.
David Ferrer and Andy Murray, the top two seeded players in the Mexican Open, advanced to the second roundwhile American and third-seeded John Isner became the first major casualty of the tournament, losing 7-6 (4) 7-6 (5) to Croatia's Ivo Karlovic.
Ferrer, the favourite in Acapulco, had a convincing 6-2, 6-3 victory over Kazakh Mikhail Kukushkin while Murray overcame a sluggish start and claimed a 3-6, 6-1, 6-2 win over Pablo Andujar, from Spain.
Murray, who played for the first time ever in Latin America, lost his first three service games and fell into a 5-0 hole, but came back strongly to set up a match against Joao Sousa of Portugal.
In the round-of-16, Ferrer, who is trying to win on Mexican soil for the fourth time in his career, will play Spanish compatriot Feliciano Lopez.
Earlier, Karlovic served 15 aces to Isner fired eight in a match between two of the game's biggest servers.
"I'm very disappointed," a visibly upset Isner said after the match. "I wanted to do well in here, is a good surface for me, but I played against a guy who played well against me".
Sousa of Portugal came back to defeat Frenchman Adrian Mannarino 1-6, 6-2, 6-2.
South Africa's Kevin Anderson downed Stephane Robert of France 6-2, 7-6 (7) and will next play America's Sam Querrey. Seventh-seeded Ernests Gulbis had a 6-1, 6-1 victory over Taiwan's Yen-Hsun Lu.
Latvia's Gulbis won his fifth career title last week in Marsella.