Ashleigh Barty has advanced to the second round of the Rogers Cup in Toronto after Oceane Dodin of France retired hurt in the opening set.
The Australian world No.57 was leading 5-0 after just 22 minutes when her 20-year-old opponent pulled the pin.
Barty, who came through qualifying to reach the tournament, will now face 16th-seeded Russian Elena Vesnina in the second round.
Vesnina beat America's Alison Riske 6-3 6-3.
Dodin, ranked 47th in the world, reached the semi-finals of the Citi Open in Washington last week, losing to eventual winner Ekaterina Makarova.
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Meanwhile, Eugenie Bouchard's mid-season nosedive continued on Tuesday as the Canadian was swept aside 6-3 6-4 by Croatian qualifier Donna Vekic at her home tournament.
Bouchard drew little inspiration from the crowd as she added to a long list of disappointing efforts in recent times, committing 32 unforced errors and seven double faults while being broken six times by a 21-year-old making a her first appearance in the main draw.
"I think I just made too many unforced errors, you know. I'm obviously a bit low in confidence right now," Bouchard said.
"It's tough to get through tough matches when you're in a moment like that."
Vekic earned a second round meeting with German third seed and former world number one Angelique Kerber.
Former world No. 1 Caroline Wozniacki opened her campaign with a 6-3 6-0 rout of Ekaterina Alexandrova.
The Dane, who captured the Canadian trophy in 2010, is still looking for her first title of the season after being in five finals.
Polish 10th seed Agnieszka Radwanska, the Rogers Cup winner in 2014, kicked off her North American hardcourt campaign with a 6-3 6-3 win over American CoCo Vandeweghe.
"In tennis you don't have easy draws - you have bad ones, or really bad ones," said Radwanska, who will next play either Hungary's Timea Babos or Canadian Bianca Andreescu.
Catherine Bellis kept Tuesday from becoming a complete washout for the United States as the 18-year-old battled back from a set down to outlast Germany's Julia Goerges 4-6 6-3 6-2.
