It took nearly three hours, but surging Danielle Collins extended her impeccable form in the second round of the Omnium Banque Nationale on Wednesday night, as she knocked out two-time champion Simona Halep, 2-6, 6-4, 6-4, in the Romanian’s return to the WTA.

No.6 seed Halep was contesting her first match since she suffered a calf tear while facing Angelique Kerber in Rome three months ago -- an absence which, on Monday, caused her to fall out of the Top 10 for the first time since January 27, 2014 (ending 373 consecutive weeks in that echelon).

But Collins was a challenging draw for Halep’s first test, and the American extended a career-best winning streak at WTA-level with a grueling two-hour and 55-minute victory over the former World No.1. Collins, coming off of her first two WTA singles titles in Palermo and San Jose consecutively, has now won her last 12 matches.

"I can't remember when I've played this many matches, to be honest," Collins said on court, after her lengthy encounter with Halep.

The marathon affair was evenly matched all the way through -- the players had exactly the same break point conversion rate, 7-for-22. Ultimately, Collins's 38 winners, many on cracking returns, overrode Halep's 31 winners, giving the American the crucial final break of service in the decider.

"Honestly, I just feel really lucky," Collins said. "Dealing with the physical stuff today after playing a lot of matches, it wasn't easy. It definitely got the best of me physically and emotionally. So just being able to hang in there, just really proud to be able to pull through."

Nevertheless, an optimistic Halep told the press she was "very positive about how I played today. A little bit unexpected because after three months that you cannot play much tennis, you come and play three hours at a very high level with someone that is winning lately matches and tournaments. So I'm really happy with the way I played." 

2016 and 2018 Omnium Banque Nationale champion Halep needed five break points before taking a 3-2 lead in the first set, but once she did that, she swept through the rest of the opening set, where she had 12 winners to just three unforced errors.

However, in a topsy-turvy second set which featured seven breaks of serve combined, it was Collins who had the last word, as she used an array of powerful returns to break Halep at love in the final game and level the match at one set apiece.

In the third set, Halep was twice up a break, but each time Collins struck back immediately. The pair found aces on game points to get to 5-4, which proved to be a classic game full of arduous, creative rallies at tense moments. Collins saw four match points disappear, but on her fifth, another great return forced an error from Halep, and the American’s winning streak survived.

After the match, Collins confirmed she hyperextended her knee twice during the match. She took a medical timeout early in the third set after feeling the pain move up to her hip and quad area.

"After playing a two-and-a-half-hour match, it would have been heart-breaking to have to pull the plug and I really wanted to get through the match, win or lose," Collins said. "I thought we were both playing such good tennis, it was such a great match."

Next up for Collins will be a fellow American power player: Jessica Pegula, who also had a three-set comeback win over a Top 10 seed on Wednesday night. Pegula eliminated No.10 seed Anastasia Pavlyuchenkova, 1-6, 6-3, 6-2, in an hour and 51 minutes to book her round-of-16 clash with Collins.

Pegula, who reached her first Grand Slam quarterfinal at this year's Australian Open, ended up converting five of her 12 break points to advance. Pavlyuchenkova, this year's Roland Garros runner-up and a Olympic gold medalist in mixed doubles, was 4-for-14 on break points as she fell just short to Pegula.

"Jessica and I haven't played since the ITF days back when we were much, much younger and she blew me off the court," Collins said. "So I'm just hoping that when I go out there I can do better than the last time."

Another three-set comeback followed Collins and Halep on Centre Court, as No.13 seed Ons Jabeur of Tunisia steered past Daria Kasatkina of Russia, 2-6, 6-3, 6-4, in two hours and eight minutes.

The clash was a rematch of this year's Birmingham final, where Jabeur at long last claimed her first WTA singles title. World No.22 Jabeur made it two in a row over 27th-ranked Kasatkina in Montreal, leveling their head-to-head at two wins each.

A breezy first set by Kasatkina was countered in the next frame by Jabeur. The seeded player dropped serve in the first game of the second set but stormed back from there, claiming six of the last seven games to tie up the match.

The Tunisian kept up her momentum in the decider, and won a difficult seven-deuce game to break for 5-2 and serve for the match. Jabeur was unable to close out the win there, but with an insurance break in her pocket, she served out the victory on her second time of asking.

Jabeur will be back on Centre Court on Thursday night as well, when she will face down Canadian hope, defending champion, and No.2 seed Bianca Andreescu in a hotly-anticipated round-of-16 showdown.

Ons Fire: Jabeur's shotmaking masterclass in Montreal vs. Kasatkina