ON "60 MINUTES" THIS SUNDAY: TENNIS GREAT RAFAEL NADAL SAYS A LITTLE DOUBT IN HIS MIND IS KEY TO HIS SUCCESS

Jon Wertheim Goes on "Vacation" with Nadal to his Hometown in Mallorca, Where He Still Practices Intensely - Every Morning

How does the world's #1 ranked tennis player stay on top? He practices intensely every morning - even at home on a break from the tennis season. Intensity is not the first word that comes to mind on the beautiful Spanish island of Mallorca, where Nadal grew up and still lives. Nonetheless, Jon Wertheim finds a focused player who tells him that a key to his remarkable and enduring success is the doubt he has in his mind and the way it keeps him sharp. Wertheim's story on Nadal will be broadcast on 60 MINUTES Sunday, Jan. 12 (7:00-8:00 PM, ET/PT) on the CBS Television Network.

Nadal has been a top-10 player on the tour since he was a teenager, and today, at 33, he has won 19 major tournaments, just one behind the men's record held by his older rival, Roger Federer. He has closed out the season as the #1 player five times.

Most players use the five weeks of tennis' off-season to rest up. It's a nice break in a beautiful place, but Nadal practices each morning in Mallorca. 60 MINUTES cameras were allowed in for a rare look at Nadal's practice session. They capture him being peppered with shots by his two coaches at the same time. Nadal pounded back with the same determination and force he would use in a Wimbledon final. "I am a very intense person with a lot of energy. I live life and sports at maximum intensity. This is how I feel it," he tells Wertheim, who has been covering him on the pro tour for 15 years.

Some of the intensity he brings to bear in his pro matches comes from an unlikely place. Whereas most players want to strike doubt from their minds to boost their confidence, he says that he draws on doubt when facing his opponents. "If you don't have doubt, it probably means that you're being arrogant," he says. "[Doubt] is good for me, because then I feel alert. Tennis is a sport where things can change very quickly. That's the great beauty of our sport."

Wertheim reports that Nadal got an early start in the sport when his tennis instructor uncle, Toni Nadal, first discovered his talent. "Normally, when you throw the ball to most kids, they wait for the ball to come to them," says the older Nadal. "But when [Rafael] was three years old, he went straight for it."

Follow 60 MINUTES on Twitter, Facebook and Instagram.