Germany's Laura Siegemund returns the ball to Spain's Paula Badosa during their women's singles fourth round tennis match on Day 9 of The Roland Garros 2020 French Open tennis tournament in Paris on Oct 5, 2020. (ANNE-CHRISTINE POUJOULAT / AFP)

Unseeded German Laura Siegemund came through a tense opening set before cruising past Spaniard Paula Badosa 7-5 6-2 to reach her maiden Grand Slam quarter-final at Roland Garros on Monday.

Up next for unseeded German Laura Siegemund is a meeting with Czech seventh seed Petra Kvitova 

Both players struggled on serve in the first set of their see-sawing fourth-round clash on Court Simonne Mathieu, with Siegemund down 5-3 before switching gears to draw level.

The German then claimed a decisive break of serve to take the early advantage in the contest between the unseeded pair.

Badosa, a former junior champion who knocked out 2017 winner Jelena Ostapenko of Latvia in the previous round and 2018 runner-up American Sloane Stephens in her second match, fell 3-1 behind in the second set as Siegemund turned up the heat.

Siegemund, pushed to three sets in her last two matches, fought off a spirited comeback attempt from Badosa to stretch the lead further with a break in the seventh game of the second set before closing out the victory in style.

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Siegemund said of Badosa, who was affected by an apparent back injury: “I think it was a tough day today. Also for her. I think she was also struggling.

“It was really cold... windy. Let’s say I wasn’t feeling my best, but managed. Happy that I got through anyway.”

Up next for the world number 66 is a meeting with Czech seventh seed Petra Kvitova who swatted aside China’s Zhang Shuai 6-2 6-4 to reach the last-eight for the first time since 2012 when she lost in the semi-finals.

“Petra’s a really tough opponent, no question about it. It’ll be totally different of all the matches I’ve played here so far,” Siegemund added.

“I played also more against clay court players, more with spin and very tactical. She’s not like that. She serves very well. There are no second chances in rallies with her.

“That will be different and I’m looking forward to it.”