Croatia's Vekic powered to a 6-3, 6-4 victory, to the disappointment of a partisan crowd whose vocal support couldn't lift Bouchard.

The Canadian, who has just one match win since a second-round exit at the French Open, committed 32 unforced errors and seven double faults.

She was broken six times by the 21-year-old Vekic, who is in the main draw of this US Open tuneup for the first time.

"I guess I am going to have to have a tournament in Croatia to finally have the home crowd," said Vekic, who booked a second-round clash with German third seed Angelique Kerber -- who held the world number one ranking earlier this year.

Bouchard, touted as a rising star when she reached the 2014 Wimbledon final on the heels of semi-final appearances at the Australian and French Opens, was once ranked as high as fifth in the world.

She's now 70th and received a wildcard entry into the main draw, but her Toronto campaign lasted just 94 minutes.

"I'm obviously a bit low in confidence right now," Bouchard said. "So it's tough to get through tough matches when you’re in a moment like that."

In second-round action, former world number one Caroline Wozniacki of Denmark, seeded sixth, powered through with a 6-3, 6-0 win over Russian Ekaterina Alexandrova.

Fifth-seeded Elina Svitolina of Ukraine also advanced with a 7-6 (7/4), 6-4 win over Russian Daria Kasatkina.

In other first-round matches, 10th-seeded Agnieszka Radwanska of Poland continued her dominance of big-serving American CoCo Vandeweghe with a 6-3, 6-2 win.

Radwanska, winner of the Canadian crown in 2014 when the tournament was held in Montreal, has won five straight hardcourt meetings against Vandeweghe -- who managed to turn the tables in a grass court clash at Birmingham last year.

It was a disappointing early exit for Vandeweghe, who reached the final at Stanford last week to move into the top 20 in the world rankings.

Russia's Anastasia Pavlyuchenkova swept past France's Alize Cornet 6-0, 6-1 to book a second-round meeting with newly minted world number one and top seed Karolina Pliskova.

Magdalena Rybarikova of Slovakia downed Croatian Mirjana Lucic-Baroni 7-5, 6-0 to line up a meeting with second-seeded defending champion Simona Halep, who won the Canadian title in Montreal last year.

Source: AFP