Latvian Jelena Ostapenko, the 2017 French Open champion, lost her opening match Monday at the WTA Montreal Masters, falling to Katerina Siniakova, the Olympic doubles gold medalist alongside Barbora Krejcikova.
The Czech posted a 6-1, 6-3 victory to reach the second round in an hour and a quarter, with Ostapenko double-faulting six times and losing her serve on seven occasions.
American teen Amanda Anisimova won a matchup of qualifiers, the world number 86 defeating Tereza Martincova 6-1, 4-3 when the Czech retired.
Anisimova has now won both of the pair’s matches, the first played in 2019 at Mallorca.
The tournament debutant was playing only her second match since a first-round defeat at Wimbledon.
“I’m feeling really good and it’s good to have a couple matches in quallies,” the 19-year-old said.
“I was playing well today. My opponent wasn’t feeling too good. I feel sorry for her.
“I’ll build on the last three matches and I’m looking forward to my next round.”
Anisimova, who has struggled with injuries in recent seasons, said she is now fully fit.
“I feel better and I feel stronger. Hopefully I can just build on that this year. I’m looking forward to this season and the US Open.”
Spain’s 31st-ranked Paula Badosa defeated Swiss Viktorija Golubic 6-2, 6-3 while France’s Fiona Ferro put out Ajla Tomljanovic 2-6, 6-2 when the Australian retired.