Friday, April 13, 2018
 Steve Johnson (USA) d  John Isner (USA) 7-6(4) 4-6 7-6(5)
Taylor Fritz (USA) d  Jack Sock (USA) 6-3 3-6 6-4
Ivo Karlovic (Croatia) d  Nick Kyrgios (Australia) 3-6 6-2 6-3
 Tennys Sandgren (USA) d Guido Pella (Argentina) 4-6 7-5 6-3
Doubles Semifinal Round
Max Mirnyi (Belarus) & Philipp Oswald (Austria) d  Bob Bryan (USA) & Mike Bryan (USA) 6-4 2-6 10-6
Andre Begemann (Germany) & Antonio Sancic (Croatia) d [WC] Dustin Brown (Germany) & Frances Tiafoe (USA) 6-3 3-6 10-7
ORDER OF PLAY – Saturday, April 14, 2018
Center Court – 1 pm Start
Ivo Karlovic (Croatia) vs  Tennys Sandgren (USA)
 Steve Johnson (USA) vs Taylor Fritz (USA)
Max Mirnyi (Belarus) & Philipp Oswald (Austria) vs Andre Begemann (Germany) & Antonio Sancic (Croatia)
– Friday was the first time in the Open Era that all four US Clay singles quarterfinal matches have gone three sets.
– Three Americans have reached the US Clay semifinals for the second year in a row and the third time since the tournament moved to Houston in 2001.
– At 39-years-old Ivo Karlovic is the oldest US Clay semifinalist in the Open Era. He’s the oldest semifinalist at an ATP event since 40-year-old Jimmy Connors at San Francisco in 1993. He is bidding to be the oldest ATP finalist since 43-year-old Ken Rosewall won in Hong Kong in 1977.
– Karlovic won the US Clay title in 2007, the final year the event was held at Westside Tennis Club. He is bidding to return to this final for the first time since. It would be the longest gap between US Clay finals appearances since the 15 years between Andre Agassi’s championship efforts in 1988 and 2003.
– Taylor Fritz, 20, is the youngest US Clay semifinalist since Ernesto Escobedo reached the final four as a 20-year-old last year. He is bidding to be the youngest to reach the US Clay final since 20-year-old Andy Roddick fell to Andre Agassi in the 2003 final.
– Defending champion Steve Johnson is bidding to be the first player to reach consecutive US Clay finals since Jack Sock in 2015-16. He’s attempting to be the first player to repeat as US Clay champion since Andy Roddick in 2001-02.
– The winner of the Johnson-Fritz match will be the first player to reach the US Clay final having played four Americans en route since Jaime Yzaga beat five straight Americans to win the title in 1991 when the tournament was held in Charlotte.
– With his 19th ace of Friday’s match, John Isner became the fourth player in ATP history to hit 10,000 aces in his career. Isner’s milestone ace came on a 138 MPH serve down the “T” on the first point of the 1-2 game in the third set. The ball from that point was immediately taken out of play and will be sent to the International Tennis Hall of Fame in Newport, R.I. Isner joins Ivo Karlovic (12,622 through the quarterfinals here this week), Roger Federer (10,463) and Goran Ivanisevic (10,131) in the 10,000 ace club. With 28 aces Friday, Isner now has 10,009 in his career overall and 392 aces in 25 career matches at River Oaks.
– Andre Begemann and Antonio Sancic have reached their first ATP doubles final together. Begemann will be seeking his fifth career title while playing in his 10th final while Sancic will be contesting his third career ATP final with hopes of winning his first title.