ROME, Italy – Greek youngster Maria Sakkari proved her clay court mettle on Thursday, winning her second match of the day to reach the Internazionali BNL d’Italia quarterfinals as No.2 seed and Porsche Tennis Grand Prix champion Petra Kvitova was forced to retire with a left calf injury, trailing, 7-5, 5-7, 4-0.

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“Petra is the most difficult player for me to play, in my opinion,” Sakkari admitted after the match. “She’s left-handed, has a big serve and big shots. You never know what she can come up, some unbelievable shots. I was doubting a little in the beginning, 0-3 down. When Tom [Hill] came on court, he gave me a little courage and I changed tactics. I’m very pleased with how I turned the match around.”

The Grand Prix de SAR La Princesse Lalla Meryem champion continued the momentum from winning her first title, ousting 2018 Rome semifinalist and Porsche Tennis Grand Prix runner-up Anett Kontaveit earlier in the day and surging towards another big win when Kvitova could no longer continue after two hours and 15 mintes on Centrale Court.

“In the first match, I’ve played Anett so many times, and we’re such good friends. She’s a very dangerous player on all surfaces. I just went on court, played my game and served well, which helped. I think I played quite solid this morning, and quite solid this afternoon!”

Kvitova was also doing double duty after Wednesday’s washout, dropping just one game to Kazakh rival Yulia Putintseva and winning the first three games to kick off her clash with Sakkari.