"It feels great," Wozniacki said on court after the win. "It's my first match back in over three years. Definitely a little rusty but what an amazing place to come back and play my first match. I love playing here in Montreal."
The former world No. 1 and 2018 Australian Open champion announced she would be returning to the sport in a first-person essay for Vogue in June. Wozniacki, 33, said she begin hitting again after her second child was born in October, and she realized how much she missed playing.
Playing on Center Court to a large and supportive crowd -- with giant letters spelling out "Bon retour Caro" hanging from the upper bowl -- Wozniacki walked out onto the court as "Sweet Caroline" played over the loudspeaker. Before play even got underway there were some signs of rust, including asking the chair umpire to clarify the length of time for the warmup. "Is there a four-minute warmup now?" she inquired.
But once the match began, Wozniacki, a 2010 champion at the event who had received a wild card for entry, looked more at ease. After being broken in the first game, Wozniacki won the next three games and took firm control. She ultimately needed 1 hour and 37 minutes to clinch the victory against Birrell, a qualifier ranked No. 115 in the world.
At the conclusion of the match, Wozniacki raised her hands in triumph over her head and smiled widely as the crowd gave her a standing ovation. She will next face Wimbledon champion Marketa Vondrousova who beat Mayar Sherif 6-4, 6-2.
Before stepping away from the game, Wozniacki had spent 71 weeks at No. 1 during her career and won 30 WTA titles. She announced her impending retirement prior to the start of the 2020 season with the Australian Open being her final event. Wozniacki cited her desire to pursue off-court endeavors, as well as to start a family with husband, former NBA All-Star David Lee, as her reasons for leaving the sport in her announcement at the time. Wozniacki has since had two children, a daughter named Olivia born in June 2021 and a son named James born in October 2022.
Wozniacki is now one of several mothers currently competing on the WTA Tour, including Victoria Azarenka, Elina Svitolina and Taylor Townsend. Having played the first match of the day on Centre Court, Wozniacki told the crowd her children were currently napping at match's end and she was happy to be able to have the rest of the afternoon to spend with them.
Wozniacki is slated to also play in next week's Western & Southern Open in Cincinnati, as well as the US Open, where she has been a two-time finalist. She received wild cards for both events. In her essay for Vogue, Wozniacki was more than confident in her chances to do well at the year's final major and beyond.
"Can I win the US Open? I think so," she said. "Can I win the Australian Open? I think so. That's why I'm doing this. And I guess we'll see what happens."
The 20-year-old from Laval, Quebec, barely left the result in doubt, taking control from the beginning and winning the match in 76 minutes in front of a partisan Centre Court crowd that steadily grew throughout the afternoon at IGA Stadium.
"I'm super happy that I got my first one here in Montreal, it means the world to me," she said. "The crowd was amazing. I felt their positivity, their emotions."
In the next round, she'll face No. 11 seed Beatriz Haddad Maia of Brazil -- who beat Fernandez in the second round in Toronto last year.
Collins will next face eighth-seeded Maria Sakkari of Greece.
The Italian qualifier, who won the tournament last time in Montreal, broke Andreescu once in the first set and fended off five breakpoints.
Giorgi then hit winner after winner in the second set, breaking Andreescu twice early to take a 4-0 lead. Though Andreescu fought back to win two games and save two match points, Giorgi held serve the rest of the way.
Giorgi takes on No. 7 seed Petra Kvitova of the Czech Republic in the next round.
In women's doubles play, Ottawa's Gabriela Dabrowski and partner Erin Routliffe of New Zealand defeated Karolina Pliskova of the Czech Republic and Donna Vekic of Croatia 3-6, 6-4, 10-8 to advance to the Round of 16.
The Associated Press contributed to this report.