NEW YORK — Ben Shelton remembers the exact phrase that sprang into his mind near the end of his first-round match at Wimbledon this year, an irksome loss to Otto Virtanen of Finland.When he led 8-5 in the fifth-set tiebreak, he looked up at the scoreboard and thought, “What is this bull———t?”Shelton had already let a two-sets-to-one lead slip away. If he and Virtanen had been playing a normal, seven-point tiebreak, rather than one of the 10-point versions that decide fifth sets, he would have already won.The American felt he should have already won. Virtanen was ranked No. 140 in the world, and Shelton, the No. 4 seed at the All England Club, hadn’t lost a first-round match at a Grand Slam in three years.But after his moment of awe at his fate that day, Shelton won just one more point. Virtanen took the tiebreak 11-9.“I was a little bit shocked because, to be honest. When I look back at the match, I didn’t feel that there were many other first-round matches at Slams in the last two years where I’ve played much better,” Shelton said in an interview this summer.It didn’t take long for the shock to fade. When it did, patterns began to emerge as Shelton analyzed the match. Mental lapses. Sub-par returning. Poor point construction on break points in his favor. Those are three large reasons why Shelton, 23, has had a mixed bag of a year. He has captured four titles, the most he has ever won in a single season, but he has also endured several early-round exits at the big-time tournaments, including two of the first three Grand Slams.Why are some tennis players better at night?Tifo SportsShelton’s father, Bryan, is a former ATP Tour player. He is also his son’s coach, and thanks to that influence, Shelton has always looked at his career through a long lens. The loss to Virtanen was a stark reminder that the innate gifts which have propelled him to stardom will likely not be enough to make him a champion.“I think I’m still a raw talent,” Shelton said. “I don’t feel I’m really as refined as any of the guys in the top 10, and I feel like I have a lot of tools that are coming along, but not quite there yet.”The question now is what Shelton does with this self-awareness.A title contender at the ongoing U.S. Open, Shelton displayed many of his familiar vulnerabilities in a 7-6(3), 6-7(5), 6-3, 6-4 third-round win over fellow lefty Denis Shapovalov, in a match that started Friday and ended just after 2 a.m. Saturday on Arthur Ashe Stadium.The first two sets were uneven on both sides of the net. Shelton and Shapovalov took turns flubbing leads and break points.