But he admits his long-term foot problem has caused pain in recent days.

The injury allowed him to play just one event in the second half of last year.

In an interview for BBC Sport after his fourth-round win over Reilly Opelka, Nadal said: "I just love playing here. My foot is holding well, but sometimes it's true in the match that I hurt.

"It's difficult to hide that, but it's nothing new. Some days are better, some days are worse, but if I had signed a paper three months ago, it would have been to be worse than how I am today, without a doubt."

Nadal is skipping next week's Miami Masters so he can ease his way gently into the clay-court season, and seemed confident his foot would not prevent him challenging for a fourth title of the year in California.

Nadal won the first tournament of the year in Melbourne, the Australian Open and then the Mexican Open. Since the formation of the ATP Tour in 1990, only Novak Djokovic had made a better start to the season.

"The beginning of the season is unforgettable - something impossible to imagine two, three months ago. Sometimes things happen that are difficult to explain, and this beginning of the season for me is one of those things," said Nadal, who also had Covid just before Christmas.

The Spaniard is now hoping to play in all of his usual clay-court events in Monte Carlo, Barcelona, Madrid and Rome before heading to Wimbledon for the first time since 2019.

"Tennis is not about how many events you play; it's about how many matches you play," he said.

"I go week by week. My goal is to play every single event, but of course I am open to make decisions like I had to do with Miami. But it is not in my plans. On clay, my calendar is going to be the same as usual.

"Last year, honestly, I didn't play Wimbledon because I was not able to walk during those weeks. For two weeks I was on the boat, and it was for me so difficult to move around the boat with my foot. But if I am in a normal shape, of course I want to play Wimbledon."

Kyrgios will be the latest man to try and end Nadal's unbeaten start to the season when they meet in the first of the men's quarter-finals in Indian Wells on Thursday.

Kyrgios, then ranked 144 in the world, famously beat Nadal in the fourth round of Wimbledon in 2014, and there have been a few flash points in their relationship since.

After Kyrgios won a tempestuous match, which concluded with a frosty handshake, in Acapulco three years ago, Nadal said the Australian lacked respect for the crowd, his rival and himself.

Kyrgios later told the 'No Challenges Remaining' podcast that Nadal is his "polar opposite" and "super salty" when he loses.

"I always had zero against Nick," Nadal said.

"I just think that sometimes he did things that were not right, but that's it. We have a good relationship since a long time ago.

"I don't look at him like an enemy or a bad guy at all. There are sometimes things that happen on court, but honestly I'm that kind of guy who forgets about things.

"I don't like problems at all. I try to stay well with almost everybody because I feel life is much happier like this."