Defending champion Carlos Alcaraz became just the second man in the Open Era (since 1968) to reach three US Open quarter-finals under the age of 21 on Monday when he moved past Italian Matteo Arnaldi. The 20-year-old Spaniard dazzled the Arthur Ashe Stadium crowd with his thrilling shotmaking, consistently drawing gasps to earn a 6-3, 6-3, 6-4 win in one hour and 59 minutes against the 22-year-old, who was competing in the fourth round at a major for the first time. “The intensity from the start to the last ball, I think I played a really solid match,” Alcaraz said. “Less mistakes. I played my game. Tried to go to the net all the time. I am really happy with the performance and I am happy to be through.” Novak Djokovic continued his march towards a 24th Grand Slam crown.Third seed Jessica Pegula and Wimbledon finalist Ons Jabeur suffered frustrating defeats in the fourth round at the US Open. American Pegula, who had been one of the favourites for the title, put in an error-strewn performance in a 6-1 6-3 loss to compatriot Madison Keys.Despite her success on the WTA Tour, the 29-year-old has yet to go beyond the quarter-finals at any Grand Slam.Last year’s runner-up Jabeur lost 6-2 6-4 to China’s Zheng Qinwen.