The Spaniard described his opponent as a "very nice person" and said that he is one of the professional tennis players he feels closest to.
"He's a nice guy, very nice person, one of the players on the tour that I feel closer to] because we are from the same age," BBC Sport quotes the 27-year-old as saying.
"We grew up in similar ways and we played when we were kids.
"Today we have the chance to be in the semi-finals of the US Open, so it's great. It's a great thing for both of us, so I'm very happy."