PHOTOS/VIDEO: Rafael Nadal's press conference after his retirement in SF at US Open 2018

Q. You have been playing so well throughout this tournament, how disappointing is it for you to end this way? When did you realize you were having difficulty out there as far as your health? Before the match or during the match?
RAFAEL NADAL: No, I had some issues during the tournament. As everybody knows, I had an issue, it was in the second or third match. Then I think was little bit better.

But, yeah, I think was 2-All in the first, 15-Love, something like this in the first set, that I felt. I said too my box immediately that I felt something on the knee. After that, I was just trying to see if in some moment the thing can improve during the match. But no, was not the day.

Yeah, I waited as much as I can. You could imagine very difficult for me to say good-bye before the match finish. But at some point you have to take a decision. It was so difficult for me to keep playing at the same time that way, having too much pain.

That was not a tennis match at the end, no? It was just one player playing, the other one staying on the other side of the court.

I hate to retired, but stay one more set out there playing like this will be too much for me.

Q. How much do you think the five-set match the other night affected your knee?
RAFAEL NADAL: No, you never know. Maybe zero, maybe yes. I was not feeling worst of my knee today before the match or yesterday when I practiced.

Q. Can you describe the pain in your knee in comparison to the other issues you've had with your knee?
RAFAEL NADAL: The knee is always very similar. When that happens, yeah, just accept it. That's all. I cannot compare the knee with other times because the pain on the knee is always very similar when I have.

The problem is this time was something little bit more aggressive because was in one movement. Was not something progressive. So I don't know what can happen in a couple of days or in a couple of weeks.

Immediately is much worst when the thing happened like this, immediately in a bad movement, than when is coming.

Q. Because of that, are you worried it might be a structural damage to the knee?
RAFAEL NADAL: Structural damage? What do you mean?

Q. That you actually did something inside the knee that hurt it, not just tendinitis?
RAFAEL NADAL: No. If I have more things, will be tough. So no, no. I know what I have. Similar thing than always. Just about do treatment. Is not an injury that tells you three weeks off and you are back. Is not an injury that tells you six months off, you are back. Is maybe an injury that in one week you feel better, is an injury that maybe in six months you don't feel better.

I know what is going on with the knee. But the good thing is I know how I have to work to be better as soon as possible because we have a lot of experience on that.

I am sure will not be the six months off. I was just making a comparation [sic]. Is not an injury like when you break something, something like this. It is an injury that is a tendinitis. Then is a decision about yourself, about if you want to wait till you feel almost nothing or you want to keep going with pain, so...

Is not the moment to think.

Q. Of course you're disappointed, but you have a great spirit and respect for Juan Martin. What does it mean to you to see him get to his first final in such a long time? His struggle has been very long.
RAFAEL NADAL: I can't say that I am happy because I am not. I will not lie you.

But, yes, he's a player that went through lot of issues during his career, like me too. I know how tough is this thing. I know how much frustration can be when you can't do the thing that you want to do. He knows very well.

Happy to him that he's able to be back in his top level. Yeah, wish him all the best. For him will be huge if he's able to win again a Grand Slam.

Q. At this point in your career, can you describe how much of your off-court work is pain management, just keeping your body in shape enough to play these five-set matches?
RAFAEL NADAL: No, I can't describe. Is just my work. Is just my normal thing of every day, just to do the work the right way, just enjoy the moments when I have the chance to play with healthy conditions.

I'm having two great years. Yeah, last year was a fantastic year. This year have been a fantastic year until this moment.

I lost four matches. Two of them I had to retired. Negative thing is two of them have been in quarterfinals and semifinals of a Grand Slam, close to fight for titles. That's frustrating. Can't tell you another thing. Is tough for me.

Is not about losing. Is about don't have the chance to fight for it. I feel that I fighted all my career against these kind of things, too. I missed lot of opportunities. But the other hand, I won a lot.

Is tough, these moments, but at the same time, on the other hand, I going to keep going and I going to keep working hard to keep having opportunities.

I know the things are going the right way. I am playing well. I am enjoying on court. I am having a lot of success. I am very competitive at the age of 32. Lot of people in this room, including myself, never will think that at the age of 32 I will be here fighting for titles, fighting for the first positions of the rankings.

All my career everybody say that because of my style, I will have a short career. I still here. I still here because I love what I am doing. I still have the passion for the game. I going to keep fighting and working hard to keep enjoying this tour and keep having chances to compete at the highest level. So that's all.

Q. When you look at the injuries that you have dealt with, Novak, Roger, Juan Martin, have as well, is this the reality of modern tennis: you're going to have to sustain these injuries to play at the level you play at?
RAFAEL NADAL: Sorry, but is not fair to compare myself with them. They didn't have a -- Novak had something last year. Roger have couple of ones. But at the age of 36 is not the same.

You can go to the history and you can compare how many Grand Slams I missed in my career, Masters 1000s, you can compare how many they missed. Sorry, but is not the real comparation [sic].

But is part of the game. I can't and will not complain. Is just something that is like this. Even like this, I am in a good sport of the history of this sport, and keep going. That's all.

Q. Is hard court particularly difficult on your knees given your injury history at this point?
RAFAEL NADAL: It's okay (tearing up).

FastScripts Transcript by ASAP Sports

Photos: USTA; ZUMA Press; BPI

• in English

• in Spanish

• Interview for Eurosport ES

"It's a tough, ugly moment. Mentally, it's very difficult to accept... I've had to retire in 2 of the 4 majors... but I just have to accept it & keep on working to have more chances" (via @genny_ss)