Rafael Nadal's superb winning streak on clay courts came to an end in the quarterfinals at Rome on Friday.
Eight-seeded Austrian Dominic Thiem ended Nadal's 17-match winning streak on clay this season be posting a dominating 6-4, 6-3 victory over Nadal at the Internazionali BNL d'Italia tournament.
Nadal won three consecutive clay-court tournaments -- including victories over Thiem in the finals at Barcelona and Madrid -- but was unable to match Thiem's aggressive level of play this time.
Thiem won the match in one hour, 51 minutes to continue his own sparkling success on clay. He has a 17-3 mark on the surface in 2017.
"I came in with a very aggressive game style, because I knew that if I wanted to have a chance, then I would have to do something different and be more aggressive," Thiem said after the victory. "I knew that if it goes in, everything, maybe I have a chance. If not, maybe I also lose easy. But today was one of these days where I really felt the ball great on the racquet, and a lot of risky shots went in.
"It was a very, very good performance and I think probably one of my best matches."
Nadal, who has won seven titles in Rome, made a second-set charge to tie it at 3-3 before Thiem broke his service to move back head. Thiem again broke Nadal in the final game, winning four straight points and the upset became official when the Spaniard hit a forehand shot wide.
The victory was Thiem's second in six career matches against Nadal.
"It's a great achievement for me," Thiem said. "If you're up a set and a break, you never feel safe because he just doesn't give you one easy point. So you really have to finish the match off, and that's what I did today with a little bit of trouble in my last service game.
"He's this kind of player who never gives up. Probably the best fighter in tennis. Especially on clay, it's one of the toughest things to beat him."
Nadal was asked what went wrong and provided a simple answer.
"What was wrong is that the other player played very well," Nadal said.
"I just have to congratulate (Thiem), because he was better than me this afternoon. He played great in all aspects. Just well done for him. It's obvious that I did not play my best match. I have been playing a lot ... so is not easy after playing almost every day for the last four weeks."
Isner delivered 21 aces to become the first American to reach the semis at Rome since Andy Roddick in 2008.
"I just felt like I kept my composure out there," Isner said afterward. "I knew it was going to be a tough match (and that) I was going to win a lot of quick points. So I knew at the very least I was going to be in the match. That's exactly what happened.
"I felt like I played well when it mattered, and it's good to win a match like that. I have certainly lost a bunch like that in the past two years, really."
Isner will meet 20-year-old German Alexander Zverev in the semis. Zverev, seeded 16th, rolled to a 7-6 (4), 6-1 win over fifth-seeded Canadian Milos Raonic.
Isner, 32, has dropped both his previous matches against Zverev.
"It's an extremely tough match. I actually know him very well, since he was very young," Isner said. "I train with him a bunch, and I played him two times and I'm 0-2. I would certainly love to get some revenge on him.
"But he's playing remarkably well, and it was only a matter of time, in my opinion, before he started having results like this."
Zverev will be playing in an ATP Masters semifinal for the first time in his career after needing just 90 minutes to dispatch Raonic. He is the first German to reach the semifinals in Rome since Tommy Haas in 2002.
"It's another stepping stone in my career," Zverev said afterward. "I feel like I have played very well today. I returned very well.
"So I'm happy to be in the semis and playing John tomorrow, who I know very well from our Saddlebrook (Florida training) days. We practice quite a lot together in the offseason and do quite a lot of stuff together. It's going to be a great match. I'm excited for both of us."