ST. PETERSBURG, Russia - Greece's Maria Sakkari authored a thrilling comeback to cap the first day of play at the St. Petersburg Ladies' Trophy.

The No.6 seed battled back from a 5-2 deficit in the third set to beat Russian qualifier Vitalia Diatchenko, 3-6, 6-4, 7-6(3), to seal a first-round victory at the Premier event in over two-and-a-half hours.

After a pair of first round exits in St. Petersburg in each of the past two years, Sakkari took the long way to her first main draw win at the event, and saved a match point when Diatchenko first served for victory in the eighth game of the set.

"Indoors suits her better than me," Sakkari told after the match. "I have to say that coming out of the match, I can't say that I got used to the conditions. She has a tricky game. She hits pretty big and pretty hard - maybe one of the fastest hitters on the tour - and two-handed on both sides, so it's quite tricky. I'm happy. It's my first win here, so I'm going to get used to the court better."

Despite never winning a set in her previous two encounters against Sakkari, one of which took place earlier this year in Brisbane, the 29-year-old Russian took command of the first round match from 3-1 down in the opener, despite nearly 70 places between the two in the WTA rankings.

The Russian won eight straight games behind flat, precise, two-handed groundstrokes that disrupted the Greek's rhythm on the indoor court.

"I think I was a little bit angry with myself in the first set after being up 3-1. She came up with some good tennis and I have to give her credit for that," Sakkari said. 

"I was down most of the time, and I was thinking that if I lose, 'Where am I going to go? Dubai, Monaco, or Athens for a few [days]?' but I prefer to stay here!"

However, from 6-3, 3-0 down, it was Sakkari's turn to go on a run, and the No.6 seed won the next four games, and six of the last seven, to send the match to its dramatic finale. 

"I know that I have a good physique, so I can rely on that," she said. "It's taking a step back, and not trying to play my best tennis. Making more balls, making the opponent kind of feel uncomfortable, that's how I try to come back in the match."

After four straight breaks to begin the third, the Russian won three straight games and served for the match twice in the decider, but racked up all six of her double faults for the set after building that edge.

The World No.89 tossed in two in the eighth game on her first attempt to serve out the match, including one on match point. Three more followed in the 10th game en route to her being broken for 5-5, and she tossed in one more - the 16th overall in the encounter - to end the match after a marathon two hours and 39 minutes.

"It's not easy to be 5-2, match point up," Sakkari said. "Especially at 5-4, when she double faulted three times, I could really feel the tension from her side. These are normal feelings and feelings that everyone gets."

Sakkari's comeback closed out a three-match Monday slate on Sibur Arena, as No.8 seed Elena Rybakina of Kazakhstan was a winner over Katerina Siniakova to begin the day and Anastasia Potapova downed Liudmila Samsonova in a battle of Russian qualifiers, 6-2, 6-4.

Up next, Sakkari will face either Alizé Cornet or Jelena Ostapenko.

"Alizé, she's a very solid player and a big fighter. We've played each other a few times. This is not easy here, because the court may not be that fast, and we can make a lot of rallies," Sakkari assessed.

"Ostapenko, sometimes it's up to her. If she's on, it's so difficult to play her. There are tactics for both opponents."

2020 St. Petersburg highlights: Rybakina races past Siniakova in opener