Rafael Nadal is 31 years old. When he first came to the hard courts of Flushing Meadows, he was 17, a European dirtballer on the rise.
Nadal is 14 years older today, and he now owns 16 more Grand Slam titles than he did then. The hair is shorter, as are the pants, but essentially, he is the same man, and the same player.
The book on Nadal, even at a young age, was that he was an extraordinarily passionate, fiercely competive and indefatigable player.
But with his relentless playing style – all the torque and pounding he subjected his body to – few thought Nadal would have an especially long career.
Sunday afternoon on Arthur Ashe Stadium, Nadal dug out balls from deep in the back court. He raced forward to hunt down drop shots. He whipped his trademark "banana" forehands. Basically, Nadal played every point as though his life depended on the outcome of the match.
The same passion. Same desire. Nothing has changed.
When Rafa made his first appearance at the Open, he was a strapping man-child. In 2003, before I'd ever seen him strike a ball in person, I stood next to Nadal in line at the player dining room in Ashe Stadium. The young man was so unfailingly courteous to the lunch ladies. He was modest dealing with the press and tournament personnel. Nadal had a definite presence, but he carried himself with a maturity that defied his teen years.
Now into his 30s, Nadal is perhaps more philosophical about the game of tennis and his role in it. But in press conferences he impresses as largely the same earnest, thoughtful and serious athlete that he has always been.
Nadal speaks frequently about the need to retain one's humility, while continually striving to improve. Prior to the quarterfinals this year, Nadal said: "Because if you believe that already, you know about everything, is tough to be enough humble, to work, wake up every morning, going on court and thinking about things you need to improve.
"Of course the talent is so important, but when you have a good talent, the most important thing is that you have the passion to improve every day and not consider yourself that good to feel that you know about everything."
Nadal is a man of thoughtful answers, about more than tennis.
After his first-round match, Nadal was asked about the recent terrorist attack in Barcelona, a city close to his heart. (Nadal is a 10-time winner of the Barcelona Open, where Center Court is named after him.) Nadal gave an unusually reflective, off-the-cuff answer.
"That's now affected to us in Spain, in Barcelona. Before was Paris and London, New York a few years ago. It's happening very often, and when happens closer to you, seems that's more important," he said. "But at the end of the day is important everywhere, because some innocent people are suffering and a lot of families and people are suffering, so is terrible."
"And it's very difficult to manage, because there is a lot of ways to create pain. Is difficult or almost impossible to control," he continued.
As was initially feared, injuries have long complicated Nadal's career. The Spaniard has missed a combined 25 months of action and been forced to sit out a half-dozen majors from over the course of his career, including Wimbledon last year; the US Open in 2014 and 2012; the Australian Open in 2013; Wimbledon in 2009; and the Australian Open in 2006.
About his injuries, Nadal said simply, "That's part of the sport." But he recognizes that "more than nobody else, I know how tough it is."
Nadal, unlike his semifinal opponent Juan Martin del Potro and many others before him, unexpectedlly has been able to reconstitute his body and game repeatedly.
After missing seven months with a partially torn patella tendon and patella tendonitis in his left knee in 2012-13, the Spaniard rebounded to win both the French and US Opens, and reclaim the top ranking, in 2013.
And here Nadal is at 31, playing some of the finest tennis of his career. Nadal won a record-setting 10th French Open, a 10th championship in Monte Carlo and Barcelona, and now his third US Open. And he has again captured the No. 1 ranking. Nadal has won majors in his teens, 20s and 30s.
"I tell you, for me what is more important, more than win Slams is be happy," he said. "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."
For Nadal, even after spending nearly half his life on the professional tennis tour, the fundamentals seem never to change.