NEW YORK: Defending champion Naomi Osaka of Japan and Greek third seed Stefanos Tsitsipas were both ousted from the US Open by 18-year-olds in epic stunners on Friday at Arthur Ashe Stadium.Four-time Grand Slam champion Osaka was shocked by Canadian left-hander Leylah Fernandez 5-7, 7-6 (7/2), 6-4 after Spain’s Carlos Alcaraz upset French Open runner-up Tsitsipas 6-3, 4-6, 7-6 (7/2), 0-6, 7-6 (7/5).”Shock followed shock as defending champion Osaka, in a tearful news conference after the loss, announced she was taking a break from playing tennis.”I honestly don’t know when I’m going to play my next tennis match,” Osaka said, wiping away tears. “I think I’m going to take a break from playing for a while.”Osaka, who had won her prior 16 Grand Slam matches, was foiled in a bid for her third US Open crown in four years and the first back-to-back titles since Serena Williams in 2014.Alcaraz is the youngest man in the US Open fourth round since 17-year-old American Michael Chang in 1989 and at any Slam since Ukraine’s Andrei Medvedev in the 1992 French Open.Osaka, who hadn’t played since Monday thanks to a second-round walkover, took the first set in 37 minutes on her sixth ace. But Osaka was broken in the 12th game of the second set, an errant forehand sending her to a tie-breaker.That began a sequence of repeated racquet smashing by Osaka as she was humbled in the tie-break to force a third set.Fernandez, the daughter of an Ecuadoran father and Filipino-Canadian mother who turns 19 on Monday, hit a forehand winner to break Osaka to start the third set.Osaka saved two break points to hold in the third game and from there both held to the finish, which came after two hours and four minutes, sending Fernandez against German 16th seed Angelique Kerber in her first Grand Slam fourth round appearance.Fernandez, who won her first WTA title in March at Monterrey, had never beaten so high-ranked a rival as third-rated Osaka and the same was true for Alcaraz when he sent home the men’s world number three. Alcaraz became the youngest man to beat a top-3 player at the US Open since the rankings began in 1973.World number 55 Alcaraz next faces 141st-ranked German qualifier Peter Gojowczyk, who ousted Swiss Henri Laaksonen 3-6, 6-3, 6-1, 6-4.Alcaraz won his first ATP title at Umag in July, becoming the tour’s youngest champion since 18-year-old Kei Nishikori in 2008 at Delray Beach.The teen nicknamed “Next Nadal” was the crowd darling at Arthur Ashe Stadium, roars erupting when he blasted 33 winners past Tsitsipas.Tsitsipas opened the final tie-break with an ace but Alcaraz jumped ahead 5-2 and 6-3 before finishing matters after four hours and seven minutes with a forehand winner. He collapsed to the court on his back to celebrate.Russian second seed Daniil Medvedev, the 2019 US Open and 2021 Australian Open runner-up, beat Spain’s 74th-ranked Pablo Andujar 6-0, 6-4, 6-3. He’s next face British 24th seed Daniel Evans.