TORONTO, Canada - No.4 seed Simona Halep kicked off her Rogers Cup title defence with a thrilling and at times arduous three-set epic against qualifier Jennifer Brady, eventually coming through 4-6, 7-5, 7-6(5) in two hours and 26 minutes to reach the third round.

"It was a very, very tough one," Halep said, during her post-match press conference. "I expected it because I knew that she's going to serve big and also the forehand is big."

In her first match since playing the "best match of her career" to win Wimbledon with a stunning 6-2, 6-2 defeat of Serena Williams in the final, Halep spent much of today struggling to approach the same accuracy or consistency. Kept at bay for large stretches of the contest by Brady's heavy forehand and strong serve, the former World No.1 racked up an unusually high total of 33 unforced errors and found herself unable to sustain any scoreboard momentum.

"I was tired in the third set," admitted Halep. "I felt the Achilles since the first point of the match. But it's normal after a break, and also coming on the hard courts. It's very difficult for the ankles and also for the knees. But I'm happy to go through, and hopefully tomorrow I will be okay."

"In my mind, it's just to get better every point, to feel the rhythm as much as possible, to fight for every ball," said the reigning Wimbledon champion. "And knowing that if I'm doing that, I have a better chance to get the rhythm back fast. So I feel like today I did a good job on court, and I'm sure that it's going to be much better day by day."

Brady made an immediate statement of intent, rocketing out of the gates with three aces in her first two service games and breaking Halep to 15 as the two-time major winner took her time in finding her rhythm. Once the Romanian had settled, she appeared to have found a winning strategy as she peppered the more error-prone Brady backhand relentlessly, and captured two consecutive deuce games to level at 3-3 - but, four holds later and serving to stay in the set, it was Halep who suddenly threw in a loose service game, with four routine errors handing the opening act to Brady.

The two-time major winner again seemed to have found her best form as the second set got under way, forcing errors from Brady with improved rallying - but, in what would be a pattern over the course of the set, was quickly pegged back to 2-2 by the battling American. Opening up the court to find some marvellous angles, Halep broke again for 4-3 - but, serving for the set, lapsed as suddenly and completely as she had to lose the first set.

On return, Halep's accuracy reappeared as she once again dominated off the ground to move up 6-5 - but it took all of the 27-year-old's fighting spirit to close the set out with a service game that could have swung either way, saving another break-back point before summoning a brilliant forehand and a fine serve to take her second set point.

As if unleashed, Halep was finally able to find her best tennis for an extended length of time, smothering the World No.76 with redirection and smart shot selection, particularly finding joy with wrongfooting plays. Sixteen of the first 20 points of the decider went Halep's way as she rapidly built a 4-0 lead.

But Halep's purple patch could not take her over the line. A handful more loose errors rejuvenated Brady, and the 25-year-old needed no further encouragement to roar back into the match. Striking her forehand with the relish she had started the match with, Brady reeled off five straight games to reach the brink of victory for the first time at 5-4.

The stage was set for an edge-of-seat climax that saw Halep showcase some of her best tennis - both in terms of tactics and shotmaking. Serving at 4-5, a shanked forehand and third double fault put Halep two points from defeat - but, buckling down to keep the ball in court at all costs, a sequence of nailbiting baseline exchanges saw the Doha and Madrid finalist grind out the hold and then break Brady for 6-5.

Once again, the qualifier came charging back with bullying forehands and sharp volleying to force a tiebreak - which proved to be a fittingly thrilling dénouement to the contest. Little separated the players until the final few points, where it was Halep who was finally able to come up with the sharp angles to come out on top on her second match point.

"I'm really pleased with the way it was today, the fact that I fought till the end," said Halep. "Even if I was 4-0 up, then I lost five games in a row, it was a little bit tough at that moment, but I felt that I have energy to turn it around and to win it."

Halep will face either Donna Vekic or Svetlana Kuznetsova in the round of 16. "Both players are playing great," said Halep. "Vekic is having a lot of confidence lately. She won many matches. Kuznetsova is coming after an injury, so at this moment she has nothing to lose, just to play her best and feeling good on court. I played tough matches against them, so it is not going to be easy at all."