The Spanish legend retired last month after battling through a number of injury problems during his final years on court but admits that the mental strain of competing was harder than the physical issues.

Nadal told The Players' Tribune: "I went through a very difficult moment mentally a few years ago.

"Physical pain I was very used to, but there were times on the court when I had trouble controlling my breathing, and I couldn't play at the highest level.

"I don't have trouble saying it now. After all, we are human beings, not superheroes.

"The person you see at centre court with a trophy is a person. Exhausted, relieved, happy, thankful - but just a person.

"Thankfully, I didn't get to the point of not being able to control things like anxiety, but there are moments with every player when it is difficult to control your mind. When that happens it is difficult to have total control of your game."

The 22-time Grand Slam winner confessed there were times that he even considered taking a break from the sport during his toughest moments.

He said: "There were months when I thought about taking a complete break from tennis to cleanse my mind. In the end, I worked on it every day to get better.

"I conquered it by always moving forward and I slowly became myself again.

"The thing that I'm most proud of is that I may have struggled, but I never quit. I always gave the maximum."

Nadal explained that he felt nervous before every match he played during his career despite his vast experience on the biggest stages.

The former world number one said: "Honestly, I have been nervous before every match I have ever played — it never leaves you.

"Every night before a match, I went to bed feeling that I could lose, and also when I woke up in the morning!

"In tennis, the difference between players is very thin, and between rivals even more.

"When you go out there on the court, anything can happen, so all your senses must be awake, alive."