ISTANBUL, Turkey - A second-round clash of former Top 5 players at the TEB BNP Paribas Tennis Championships Istanbul found qualifier Eugenie Bouchard stun No.1 seed Svetlana Kuznetsova 7-6(3), 6-7(5), 6-2 in a two-hour, 50-minute epic full of wild momentum shifts.

It is the Canadian's first win over a Top 30 player since defeating Carla Suárez Navarro in the second round of Luxembourg 2018, the last time she reached the semifinals of a tournament - and her first win over Kuznetsova at the fourth go. Previously, Bouchard had garnered just one set in three previous meetings, and only nine games in two clay encounters, with the Russian.

Today would be by far their most dramatic and least predictable match: Bouchard let a 5-3 lead and two set points slip in the first set before closing it out in a tiebreak, squandered a 4-1 lead and three match points in the second set as Kuznetsova mounted a fightback, but recovered to win the first 13 points of the decider en route to sealing her third quarterfinal berth of 2020.

"That was extremely tough mentally," said a relieved Bouchard afterwards. "I honestly just tried to not think about [losing a lead] at all, to block it from my mind - because if I did think about it I would be frustrated and angry, and that wasn't going to help me. I literally tried to have amnesia and forget about it."

It continues a solid season at WTA level for the World No.272, who also made the last eight in Auckland and Prague - and the rollercoaster scoreline in fact replicated her win over Tamara Zidansek in the second round of the latter, a match in which Bouchard also led by a set and 4-1 before needing a decider for victory.

Read more: Bouchard delivers Zidansek payback in Prague epic

"The exact same score?" Bouchard laughed when informed of this. "Oh my God, that's crazy. That's not good, that's a pattern? At least I'm coming out on the winning side. I honestly was not thinking about that match, I was just pissed at myself for... backing off with my tennis - I think that's why I ended up losing the second set.

"I blocked out mentally that I had missed match point opportunities, so I had this anger - but I was calm. I had this calm anger at the start of the third set. That motivated me - I wanted to do the right thing after messing up. I wanted to make things better."

Kuznetsova, playing her first tournament since reaching the Doha semifinals in February, initially showed little rust, slamming a forehand winner on the first point and keeping her game watertight through the six straight service holds that opened the match. But Bouchard, injecting pace judiciously and maintaining a first serve percentage of 75%, did not allow the Russian to gain any foothold on return - and in the seventh game, her depth of shot elicited a spate of Kuznetsova errors, with a shanked forehand from the World No.34 sealing the break.

Closing out the set, Bouchard took the first of several scenic routes today. The 26-year-old squandered two set points on Kuznetsova's serve, the second after missing a straightforward pass off a poor approach from her opponent, and promptly failed to serve out the opening act on her own racquet. Kuznetsova, having levelled at 5-5 courtesy of some wild all-court hustle, was in the ascendancy - and seemed to have even more momentum after chasing down a dropshot to save a break point en route to holding for 6-5 and building a 2-0 lead in the tiebreak with smart net play.

But it was Bouchard who made all the right shot choices as she recovered to reel off seven of the last eight points of the set. An ace got her on the board and a fine forehand volley levelled the tiebreak; by contrats, trailing 3-4, Kuznetsova opted to run around a forehand she was unable to put away, leaving the entire court open for Bouchard to redirect the ball into, and then double faulted to bring up another batch of set points for the former World No.5 - this time, taken with alacrity courtesy of a service winner.

Piling on the pressure, Bouchard stuck to her aggressive strategy to leap out to 4-1 in the second set over a Kuznetsova now descending all too often into error - and, having saved a break-back point to seal that lead with a superb backhand winner and an ace, appeared to be in the driver's seat again. However, the two-time Grand Slam champion came up with a brilliantly angled return to prevent Bouchard from reaching 5-2 - and slowly but surely, began to grind her way back in.

Kuznetsova would hit top form to level at 4-4, but a resilient Bouchard was still able to hold and come within a point of victory three times on the 35-year-old's delivery. But her forehand went long on the first before Kuznetsova won a marvellous all-court exchange and found an inside-in forehand rocket to save the next two, setting the stage for a tense conclusion to an unpredictable set. The ensuing tiebreak would be littered with errors from both - interspersed with the occasional drive volley as they forced themselves to remain aggressive - but, facing set point for the first time, Bouchard coughed up just her second double fault of the day.

But the 2014 Wimbledon runner-up is becoming used to these wild trajectories - and as the decider got under way, it was she who took firm control. An inexplicably deflated Kuznetsova squandered all of her momentum with a series of cheap unforced errors as Bouchard rattled off the first 13 points of the set for the first double-break lead of the match.
Kuznetsova would briefly threaten yet another swing as she found a flurry of flashy forehands to get one of the breaks back, but this time the ground would be too much to make up. Bouchard, determinedly making her way forward to pound away drive volleys, was intent on not letting this lead slip - and, having made her way to a fourth match point with an exquisite dropshot, slammed down a service winner to seal victory.

2020 Istanbul highlights: Bouchard battles past Kuznetsova