John Isner (USA) vs.  Steve Johnson (USA)
They were tied at four wins apiece; thus, tonight’s match could have gone to either player. Understandably, with both players having a big serve, the first set went to a tiebreak. The first mini-break went to Johnson and that was all he needed to take the first set.
Isner served brilliantly for most of the match and that won him the second set. Unfortunately, when he needed his serve most, it failed him in the third set tiebreak. Johnson got two mini-breaks and hung on to win 7-6(4), 4-6, 7-6(5). Isner lost the match even though he never lost his serve. Johnson is still on course to defend his title.
 Jack Sock (USA) vs.  Taylor Fritz (USA)
Sock had won both previous encounters; however, both matches went to five sets. How would Fritz fare in a three set match? Fritz came out ready to perform and Sock seemed out-of-sorts; the end result, Sock was broken. Yet, Sock can turn things around when he puts his mind to it and being the more versatile and better mover, he did just that in the second set. When he went up an early break in the third set, it seemed that Fritz was destined to lose for the third straight time. However, Fritz is mentally strong and fought back once again to win 6-3, 3-6, 6-4.
 Nick Kyrgios (AUS) vs.  Ivo Karlovic (CRO)
All four previous encounters had been won by the Australian; however, today’s encounter had an unanticipated variable, Kyrgios’ injured right elbow. It did not seem to affect him early in the match when he quickly won the first set; however, early in the second set he started grimacing after a shot and shortly thereafter, he was broken. Although he took a medical timeout after dropping the second set, it was all to no avail. Hampered by the injury he lost pace on his serve and his forehand went awry. Karlovic came back to win 3-6, 6-2, 6-3.
 Tennys Sandgren (USA) vs.  Guido Pella (ARG)
It was the first meeting for the American and he came pretty close to saying goodbye to the tournament. Pella knows how to play on clay and he had Sandgren doing everything he could to stay with him. Yet, the American was not deterred. Sandgren went down an early break in the third set; however, he fought back to defeat his opponent 4-6, 7-5, 6-3 to make his first ATP World Tour semifinal.
INTERESTING TIDBIT: all four quarterfinals went to three sets.
SOURCE OF IMAGE: Zimbio.com (Matthew Stockman/Getty Images North America: Steve Johnson)