PALERMO, Italy -- Kristyna Pliskova notched the biggest upset of the first day of main draw play at the Palermo Ladies Open, as the Czech ousted No.3 seed Maria Sakkari of Greece, 6-4, 6-4, to reach the second round of the clay-court event.

World No.20 Sakkari had won their only prior encounter on the grass of Wimbledon in 2017, but it was World No.69 Pliskova who avenged that result in Sicily on Monday, wrapping up victory after 87 minutes of play. It was Pliskova's seventh win over a Top 20 player in her career.

Photos: Tennis is back: Images from opening weekend in Palermo

In a tilt which started after midnight, the left-handed Pliskova was impeccable on serve, facing only three break points in the clash -- all coming in a single game -- and fending all of them off. The Czech won 81 percent of points off of her first serve, while breaking Sakkari in the opening game of each set to ease to victory.

"The conditions were really tough," Pliskova told the press, after the late-night win wrapped up at around 2:00 in the morning. "Before the match, I was also sleeping a little bit! We stayed so late here, I think it’s tough for [Sakkari] as well.

"The body is not used to playing at 2am, But I think my serve was there, like almost always, and it helped me quite a lot."

Pliskova broke Sakkari in the opening game of the match, and maintained that advantage for the remainder of the first set, holding for 3-1 with back-to-back service winners. Sakkari held her next two service games at love, but was unable to pull her way back level as Pliskova was unbothered on serve.

Serving at 5-4, the Czech zipped to triple set point after a forehand dribbled over the net for an unreachable winner. On her second set point, another forehand winner sealed the one-set lead, which Pliskova obtained without facing a break point.

Pliskova opened the second set in a similar manner as the first, blasting a forehand return winner down the line to set up break point, then earning the break lead after a single game once Sakkari fired a backhand wide.

Sakkari came very close to tying up the second set right away, as she finally saw her first three break points in the subsequent game. But three stellar serves by Pliskova helped the Czech stave the trio of chances off, and after the fourth deuce, Sakkari misfired on two points in a row to let Pliskova off the hook and go ahead 2-0.

Sakkari was up 15-30 at both 3-2 and 4-3, but that would be as close as she would get on Pliskova’s serve for the remainder of the match, as the unseeded player stayed steely. At 5-4, Pliskova converted her second match point after another strong serve was returned wide, and the upset victory went her way.

"I did so many points with my serve, and also my backhand was okay," Pliskova concluded. "I think of course she didn’t play her best today, like she’s playing normally on clay, but I was solid."

Pliskova will next meet two-time Palermo champion Sara Errani, who claimed a grueling three-set victory over Sorana Cirstea of Romania. Former World No.5 Errani needed nearly three hours to quell the fight of Cirstea earlier on Monday, and set up her first meeting with Pliskova.

"[Errani is] at home here, so for sure the people will cheer for her," said Pliskova. "She had quite a tough match today, I saw. It’s very different from today, but I will try to hold my serve and hopefully I will also break her!"

2020 Palermo highlights: Pliskova powers past Sakkari