The ace attack of John Isner failed to trouble Dominic Thiem as the Austrian third seed advanced to the Madrid Masters semi-finals 3-6, 6-3, 6-4 on Friday over his American opponent.
Thiem, playing his first event in six weeks after taking time off court, blunted the 18-ace output of Isner, with the two-time tournament finalist completing the victory with just two aces and the same number of service breaks.
The third seed started reversing his losing momentum while trailing a set and 2-2 in the second, saving four break points and winning five of the next six games to square the match.
A break for 5-4 in the penultimate game of the third set sealed the win in just under two hours.
“John’s serve is so tough to return and I had to find a good returning position,” Thiem said.
“Luckily, there is a lot of space here in Madrid. I used all of that and the break in the third came at the right time.”
The reigning US Open champion added: “We all know that he is one of the best servers in history and the altitude here in Madrid makes it even tougher to return his serve.
“If you start a break down against guys like John, it is like starting a set down.
“The momentum of the whole match changed when I saved those four break points in the second.”