Kicking off a tournament as top seed for the third time this season, Aryna Sabalenka battled back from the brink of defeat against a resurgent Sloane Stephens and advance to the third round of the Omnium Banque Nationale in Montreal, 7-6(4), 4-6, 6-4.

Two games away from losing her opening match for the fourth time in 2021, Sabalenka rallied to win the last five games and complete the comeback in 2 hours and 25 minutes.

"It was a tough match and she played so well. She pushed me like crazy in this match and I don't know actually how I won this won this one," Sabalenka said in her on-court interview.

"I'm really happy with this win. I was already in the locker room thinking what was going to happen next - doubles here, planning for the next weeks. I don't know if that's why I cooled down, and I was just playing and didn't think about anything else."

After sprinting out to a 4-1 lead in the opener, things got complicated for the top seed in her first match against Stephens in four years. The American, a wildcard in the field at her current ranking of World No.70, won three straight games to level at 4-4, and later saved a set point serving in the 10th game, as the set extended to just short of an hour.

A second 4-1 lead, this one in the tiebreak, proved a big enough cushion for Sabalenka to finally wrap up a one-set lead.

Neither player lost serve in the second set until Stephens broke to win it, a stretch of games which had previously seen Sabalenka save four break points to level at 3-3.

The American's momentum quickly swelled to start the decider, with her world-class counterpunching frustrating and increasing erratic Sabalenka: after saving two break points in the first game, she opened up lead of 3-0 and 4-1, moving games away from her third Top 10 win of the year. 

"I was already in the locker room thinking what was going to happen next - doubles here, planning for the next weeks!"

- Aryna Sabalenka on being down 4-1 in the final set.

Nonetheless, Sabalenka surged with her back against the wall and captured the last five games to seal victory in a thriller, erasing a break point that would've seen Stephens level at 5-5. 

In all, she racked up 45 winners to 50 unforced, while Stephens also posted a quality line of 25 winners to just 10 miscues. Among those winners, Belarusian tied a career-best mark by racking up 18 aces in victory, the third time in her career she's hit that many.

She matched that last month in the semifinals of Wimbledon in a loss to Karolina Pliskova, and in winning the title in Wuhan over Alison Riske in 2019. 

Sabalenka advances to face another big server in resurgent Canadian Rebecca Marino, also a wildcard. The former World No.38 is playing in her nation's signature event for the first time in 10 years, and after beating No.16 seed Madison Keys in the first round, rallied from a set down to beat Paula Badosa, 1-6, 7-5, 6-4.

Read more: Marino writing 'a new chapter' after back-to-back upsets in Montreal

While Sabalenka avoided the upset, the same could not be said for No.3 seed Elina Svitolina, playing her first match since capturing the bronze medal in Tokyo.

Svitolina, the champion in Montreal in 2017, entered her second-round clash with British No.1 Johanna Konta with a perfect 5-0 head-to-head record and took a one-set lead, before Konta rallied for the 3-6, 6-3, 6-2 victory.

"That was definitely not an easy match. I've never beaten her in my career, so for me personally, this was a massive win," Konta said. "She's probably the toughest player for me on tour so I'm quite pleased with myself."

For her part, Konta was contesting her first match in the six weeks since lifting the trophy in Nottingham. Withdrawn from Wimbledon as a close contact when a member of her team test positive for COVID-19, Konta herself tested positive days later and was forced out of the Olympics.

"I think the most important thing is to play with what you have and keep trying to find the little bits that you can fo better during the match," Konta added.

"That, by no means, was a perfect match from me or from her, but it was just about playing what we had. I was just able to find the solutions at the right time."

Konta will next face No.15 seed Coco Gauff for a place in the quarterfinals. The American advanced to the third round after just 22 minutes on court when Anastasia Potapova retired trailing 5-0 with injury.