As a 16th grand slam title looms for Rafael Nadal at the US Open, happiness is what matters to the Spanish world number one.

Top seed Nadal produced a stunning rally to blitz 2009 champion Juan Martin del Potro 4-6 6-0 6-3 6-2 in Friday's semi-final at Flushing Meadows.

Nadal – the French Open winner – will contest his third slam final of the year against South Africa's Kevin Anderson, and the 23rd of his illustrious career.

But there are more important things to the 15-time major champion, given the 31-year-old's run of injuries in recent years.

"For me what is more important, more than win slams is be happy. I am happy if I am healthy and happy, if I feel competitive in the most of the weeks that I am playing, and that's what happened this year," Nadal, who has two US Open crowns to his name, said. "So I am very happy about what happened, very happy to win Monte-Carlo, Barcelona, Madrid and Roland Garros. I am very happy to be in the final here in the US Open.

"Of course winning or losing that final is a big change, but I am very happy about all the things that happen to me and I am going to fight to win another title here. But still a great season for me. 

"As I tell you before, for me, more than winning grand slams or not, of course, if I win, I will be more happy but is about being healthy and feel myself well and competitive. That's already happened in the whole season. That's most important thing for me."

It was a crushing display from Nadal, who was forced to take a backseat to the power and precision of the 24th-seeded Del Potro in the opening set.

Del Potro had saved two match points against Dominic Thiem in the last 16 and stunned Roger Federer in the quarter-finals, but Nadal reeled off nine successive games to claim a second-set bagel and complete control of the match on Arthur Ashe stadium, where Tiger Woods and Leonardo DiCaprio were in attendance.

"Important day for me," Nadal told reporters. "Important victory against a great opponent. He came to that match with confidence after beating Roger, Dominic, too. A lot of the matches he played this tournament have been a tough one. But at the same time, I think I played a solid match.

"After the first set I changed it a little bit, changed my tactic, strategy change a little bit. And that makes the difference.

"I was not feeling bad the ball the first set, but I was wrong in the way that I was trying to play. When the match was coming, I started to understand a little bit better what I needed to do to try to be a little bit more unpredictable, because he was waiting for me in his backhand side.

"He was not moving from that side, so, yeah, I have to cover full court. He only had to cover 60 per cent of the court most of the time. So was a big advantage for him. Then I decided to change completely to play much more forehands down the line, and then I was more unpredictable and he was more in trouble, because he didn't know where to go.

"He arrived much more times running to his backhand, that then when he arrives running to his backhand is completely different than when he is waiting the ball there.

"And then, I don't know the statistics, I didn't see it, but I don't feel I make many mistakes after that first set, and I really hit good winners. I served well. I served really well. In general terms, have been a great match. I'm very happy with the way I played."