Top-seed Ben Shelton beat Brandon Nakashima 7-5, 7-6 (9) on Friday to advance to the semifinals of the U.S. Men´s Clay Court Championship. “Definitely not an easy matchup today with the way Brandon was serving and playing,” Shelton said. “He made things really difficulty and I was definitely feeling the pressure in that tie-break. But I´m really happy to get through.” The 21-year-old Shelton advanced to his fifth tour-level semifinal and improved to 17-1 against players outside of the top 50 in the ATP Rankings since the ATP Masters 1000 in Toronto in August. Shelton will face fourth-seed Tomas Martin Etcheverry, last year´s runner-up, in the semifinals. Etcheverry led Michael Mmoh 6-3, 0-1 when Mmoh retired because of an injury. This will be the fourth ATP tour semifinal for Etcheverry, which all of them coming on clay. In other quarterfinal action Friday, defending champion Frances Tiafoe advanced with a 7-6 (8), 6-4 victory over Jordan Thompson. “I thought it was a really good match tonight,” Tiafoe said. “First set was crucial, really, really tough. He broke me there at 5-5, I played a great game to break back. I was down in the tie-break most of the time and got out of there, and I played a pretty good second set. It was a long two-set match, but I´m happy to be in the semis here once again.”