STUTTGART, Germany - In a first-round battle of unseeded players, Anastasia Pavlyuchenkova got the better of Madison Keys in a titanic two hour, 45-minute epic 7-6(7), 5-7, 6-4.

The victory marks just the 26-year-old's third WTA victory of 2018, and is revenge for her loss to Keys in the pair's only previous meeting, in the quarterfinals of Montréal in 2016.

"I think we both played really good and it was a very even match," Pavlyuchenkova said after the match. "It was just about a few points in the end. I just tried to stay focused on every ball, every point and hang in there. I'm so happy it worked.

"I know Madison is a tough opponent. Her serve is very good. There are not a lot of girls on the tour who can serve like her. I actually was proud today, I played very consistent."

The Russian made the early running, getting the first break to edge in front in the first set, but the American got the break back to level up at 4-4, and then held her serve to move in front.

Pavlyuchenkova was not to be deterred, with another impressive service game to hold and level once more, and the tiebreak was inevitable.

It was the Russian who edged it, 9-7, taking the first set after Keys handed her set point with a double fault.

"There are a lot of good level matches because since the first round here you get [a match that could be] a quarterfinal of a Grand Slam," the Russian expounded after the match. "For me, personally, I took it as a challenge. I knew it’s such a tough tournament. I knew I’m almost the last one to get in in the main draw basically. 

"I’ve done good work for now for a couple of months. It’s a tough year for me but, you know what, I said I’m working hard and that’s a good challenge. I want to try here and that’s what I’m doing."

Pavlyuchenkova made the early breakthrough again in the second set, breaking the Keys serve in the second game.

Again the American came straight back at her, with a break and a hold to make it 2-2, and the pair exchanged breaks throughout the rest of the set - until Keys held at 7-5 to force a decider.

After an early exchange of breaks, the third set would also be dominated by the server: from 2-2 to 4-4, each player would face, and fend off, just one break point.

Throughout the match, Pavlyuchenkova and Keys both walked the power tennis tightrope, searching for the right balance between their winners and errors - and ultimately, it was the World No.27 who kept the tighter ship.

"It's very slippery court, and I knew it would be like this, so I was quite ready for it," Pavlyuchenkova assessed. 

"I played Fed Cup last week in Russia, and the surface was quite similar, so I think I was ready for it."

Though the American would slam the greater number of winners with 53, she would also concede 46 unforced errors - including four in the final game.

Pavlyuchenkova, meanwhile, was able to hit 34 winners while also keeping her errors to just 35, and would prove to be the more clutch player in capturing eight of the final 10 points of the match.

"I was expecting a lot of winners today from her, and a lot of aces, and when they were happening, I was just like, 'Okay, next one.' I accepted it and tried to stay solid still and not pay attention to that," the Russian added.

"She's a great player and I knew it would be tough, so I'm very happy that I managed to win this match."

The marathon win for the Russian sets up a second-round clash with No.2 seed Garbiñe Muguruza.