US teenager Frances Tiafoe came tantalizingly close to a stunning US Open upset on Monday, only to be denied by compatriot and five-set master John Isner.
 Tiafoe, an 18-year-old who received a wild card into the draw of the final Grand Slam of the year, won the first two sets and served for the match in the fifth before the 31-year-old Isner sealed a 3-6, 4-6, 7-6 (7/5), 6-2, 7-6 (7/3) victory.
 The match enthralled the crowd at the brand new Grandstand court, part of the $600mn remodel of the Billie Jean King National Tennis Center in Flushing Meadows.
 “Serving for it I thought I definitely had it,” said a disappointed Tiafoe, the son of immigrants from Sierra Leone. “I definitely thought the match was over, but he played a good return game. Didn’t make that many first serves that game. Probably should have played a higher percentage, but it’s tough, toughest loss of my career so far for sure.”
 Tiafoe, ranked 125th in the world, was playing in just his third Grand Slam main draw match. He broke the big-serving Isner in the veteran’s first service game and broke him twice more en route to a two-set lead over his 31-year-old opponent.
 But after Tiafoe broke for 5-3 in the fifth, Isner’s experience paid off. “If I could replay that, probably wouldn’t have gotten as hyped up when I broke,” Tiafoe said. “Maybe would have taken a little bit out of it. I think (experience) played a little part in it.”
 Isner, who was playing the 22nd five-setter of his career, had a long hug at the net for his young rival, who was playing his first. “He’s a hell of a player and a class act,” Isner said.
 Added Tiafoe: “The last thing I heard him say is ‘Don’t let this get you down.’”
 Tiafoe is among the young prospects tipped to end the decline in US men’s tennis. The last American man to win a Grand Slam title was Andy Roddick at the 2003 US Open. This year’s field include 13 American men, led by 19th-seeded Steve Johnson, 26, and 20th seed Isner.
 Experienced Sam Querrey, who shocked Novak Djokovic at Wimbledon, is seeded 29th while Jack Sock, the 23-year-old seeded 26th, stopped 18-year-old fellow American Taylor Fritz 7-6 (7/3), 7-5, 3-6, 1-6, 6-4.
 Although he and Fritz came up empty, Tiafoe said he believed the youngest US pros now challenging on the ATP Tour are capable of establishing themselves on the world stage.
 Ryan Harrison, the 24-year-old who came through qualifying along with his 22-year-old brother Christian, reached the second round with a 6-4, 7-6 (7/5), 6-3 victory over France’s Adrian Mannarino.
 “For American tennis, I think it’s looking really good,” Tiafoe said. “I think we have a lot of guys that are going to be very good. I think American tennis is definitely on the right path. We just got to keep our heads down and keep doing the work and I think we’re going to have good careers.”