Marco Cecchinato pulled off a huge upset by beating Novak Djokovic in four sets. ERIC FEFERBERG/AFP/AFP/Getty Images Djokovic received a medical timeout after the first set and lost the second in a tiebreak. ERIC FEFERBERG/AFP/AFP/Getty Images After saving three match points, he couldn't save a fourth and exited to the 72nd-ranked Italian. CHRISTOPHE ARCHAMBAULT/AFP/AFP/Getty Images Cecchinato next faces the man with the most clay wins this season, Dominic Thiem. THOMAS SAMSON/AFP/AFP/Getty Images Thiem beat second-seed Alexander Zverev, who was playing in a maiden grand slam quarterfinal like Cecchinato. CHRISTOPHE SIMON/AFP/AFP/Getty Images Zverev also received a medical timeout for a left leg injury. He struggled with his movement and lost in under two hours. THOMAS SAMSON/AFP/AFP/Getty Images In the women's draw, Madison Keys still hasn't lost a set. She beat 2016 quarterfinalist Yulia Putintseva. Cameron Spencer/Getty Images Europe/Getty Images CHRISTOPHE ARCHAMBAULT/AFP/AFP/Getty Images Keys plays fellow American and friend Sloane Stephens, who beat Daria Kasatkina -- another first-time slam quarterfinalist -- in two sets. CHRISTOPHE SIMON/AFP/AFP/Getty Images Stephens and Keys faced off in the US Open final in September, with Stephens prevailing in straight sets. Abbie Parr/Getty Images North America/Getty Images Prev Next