Spain’s Carlos Alcaraz in action during his US Open match against Lloyd Harris of South Africa on Thursday at Flushing Meadows, New York. NEW YORK: Carlos Alcaraz and Daniil Medvedev moved quietly into the third round of the U.S. Open on Thursday while big-hitting American John Isner delivered his trademark stack of aces in taking his final bow at Flushing Meadows. Alcaraz entertained a record crowd at Arthur Ashe Stadium with a 6-3 6-1 7-6(4) win over Lloyd Harris but the match also revealed a lack of sharpness which the Spaniard will need to rectify if he is to successfully defend his U.S. Open crown. Some dazzling shot making from the world number one had the crowd on its feet but Alcaraz also piled up 29 unforced errors and showed a lack of concentration at key moments. The 20-year-old will need to improve with rival Novak Djokovic on the prowl for a 24th Grand Slam and seeking revenge for his Wimbledon loss to the Spaniard. Medvedev survived a late night fright before taming Australian battler Christopher O’Connell 6-2 6-2 6-7(6) 6-2. After strolling to a two set-lead Medvedev had looked headed for routine passage but in the end the third seeded Russian needed all his resolve to push O’Connell to the exit. Isner, the standard bearer for American men’s tennis during some barren years, never made it past the quarter-finals in 17 U.S. Opens but his towering presence and booming serve made him a crowd favourite. He signed off his professional singles career with a 3-6 4-6 7-6(3) 6-4 7-6(7) loss to fellow American Michael Mmoh but did not go quietly, adding 48 more aces to his record total. Along with his thundering serve Isner is remembered for winning the longest professional tennis match in history against Frenchman Nicolas Mahut at Wimbledon in 2010, which lasted 11 hours and 5 minutes and took place over three days. There will still be plenty of American content in the third round as third seed Jessica Pegula romped to 6-3 6-1 win over Romania’s Patricia Maria Tig and Madison Keys, the losing finalist in 2017, enjoying a 6-1 6-2 win over Belgian Yanina Wickmayer. The British charge at the U.S. Open will carry on without 2012 champion Andy Murray, who was outclassed by Bulgarian Grigor Dimitrov 6-3 6-4 6-1. Known for his grit and warrior sprit, the 36-year-old Scotsman appeared to have little left in the tank on a broiling Arthur Ashe Stadium court and had no answer to the 19th seed’s firepower. Women’s second seed Aryna Sabalenka dished out more pain for British fans by knocking out Jodie Burrage in straight sets. But it was not all bad news as 16th seed Cameron Norrie, 26th seed Dan Evans and Jack Draper, with a 6-2 6-4 7-5 upset of 17th seed Hubert Hurkacz, moved onto the third round. Tunisian fifth seed Ons Jabeur, looking to return to the final and atone for last year’s loss to Iga Swiatek, is through to the third round but was made to work hard by Czech teenager Linda Noskova before sealing a thrilling 7-6(7) 4-6 6-3 victory.