ISTANBUL, Turkey - No.2 seed Svetlana Kuznetsova held off a spirited effort from Bulgarian qualifier Viktoriya Tomova to keep her campaign at the TEB BNP Paribas Istanbul Cup alive on Wednesday, winning a 7-5, 4-6, 6-1 second round clash to reach the last eight.

Kuznetsova entered the day as just one of two seeded players left in the bottom half of the draw, and after a first round victory for Aleksandra Krunic over No.5 seed Ekaterina Makarova to start the day's play, she needed two hours and 31 minutes to ensure one would reach the quarterfinals. 

The two-time Grand Slam champion saved two break points on serve in the 10th game of the opener before snatching it on her first chance, and nearly pulled off an escape to win in two as the World No.165 lead 4-0 in the second set before breaking for a fourth time to send the match the distance.

The last five games of the match all went the Russian's way, however, as the World No.28 broke Tomova's resistance with some classic claycourt tennis after the two traded breaks to start the set. 

The 23-year-old Tomova won just the third WTA main draw match of her career in Tuesday's first round against fellow qualifier Valentyna Ivakhnenko, and was bidding for her best career win in terms of ranking.

She had previously defeated then-World No.40 Julia Goerges via a retirement in Bastad last year for her lone victory in 13 career attempts against a Top 100 player. 

It was Kuznetsova who made the brighter start against her relatively inexperienced foe, breaking in a tight third game on her four opportunity to lead 2-1 at the first true changeover.

From there, however, the World No.162 proved more than equal to the former World No.2 off the ground, and twice came from a break down to stay in touch in the opener.

Though she surrendered the opener in its late stages, the qualifier proved undaunted to begin the second set. Tomova saved a break point in her opening service game, and routinely came out on top in extended baseline rallies to move ahead by a pair of breaks and build a 4-0 lead.

Kuznetsova seemingly righted the ship, winning 12 of the next 16 points to get the set back on serve, but ultimately the mettle of the qualfier sent her through to a decider.

The Bulgarian unleashed some fearsome groundstrokes to secure her fourth break of the set only to earn it with a stroke of luck, as her forehand clipped the tape and fell on Kuznetsova's side on set point. 

Kuznetsova will next face the winner of the match between Slovenia's Polona Hercog and Ukraine's Kateryna Bondarenko, as the latter avoided an upset bid on Wednesday by Turkish teenager, wildcard and World No.612 Ipek Oz, 4-6, 6-4, 6-0.