Serena Williams booked a place in the quarter-finals of the US Open on Monday with a hard-fought, three-set win over 15th seed Maria Sakkari. Serena required two hours and 28 minutes to defeat the 25-year-old Greek player 6-3, 6-7 (6/8), 6-3.

Earlier, Australian Alex de Minaur tamed Canada’s Vasek Pospisil 7-6(6), 6-3, 6-2 to ease into his first Grand Slam quarter final.

On Sunday, Naomi Osaka stood firm after a parade of champions exited, blasting her way into the quarter finals with a 6-3, 6-4 win over Estonian Anett Kontaveit.

Osaka’s left thigh was heavily strapped as she continues to manage a hamstring injury but the 22-year-old moved superbly against Kontaveit to set up a clash against unseeded American Shelby Rogers.

World No. 93 Rogers was courage personified as she saved four match points before knocking out twice Wimbledon champion Petra Kvitova 7-6(5), 3-6, 7-6(6).

Kazakhstan’s Yulia Putintseva reached the quarter finals with a 6-3, 2-6, 6-4 victory over eighth seed Petra Martic.

Alexander Zverev slammed down 18 aces en route to demolishing Alejandro Davidovich Fokina 6-2, 6-2, 6-1 in the fourth round. The German produced 39 winners and dropped just one service game during a ruthless performance.

Davidovich Fokina grabbed a 2-0 lead in the second set but the advantage was shortlived as Zverev broke back before racing away with the set. The Spaniard barely had a chance to make an impact on the world No. 7’s serve, the fastest clocking at 139 mph, just shy of his personal record of 142 mph.

Denis Shapovalov reached his first Grand Slam quarter-final with a 6-7(0), 6-3, 6-4, 6-3 win over David Goffin.