In a piece of good news for the tennis player who has struggled through an injury-plagued 2014, Nadal will feature in Hilfiger's 2015 autumn underwear and tailored clothing advertising campaigns.

Industry sources say the deal between the two long-term friends could net the world's number three up to $4 million (€3.2 million), Women's Wear Daily reported.

This won't be the first time Nadal has stripped to his smalls to give his healthy bank balance a nice little boost. In 2011, he appeared in campaigns for Emporio Armani Underwear and Armani Jeans.

Speaking about the deal Hilfiger said Nadal would have input into the designs of the clothes he will be wearing in the company's campaigns.

The designer also said Nadal would sport his clothes in his free time: “Whenever he wears a suit, he’ll wear our suit."

For his part, the tennis player feels his sense of style is a perfect fit with the preppy US brand.

"I’m a classic guy. I like to wear jeans, polo shirt, normally. To go out, it depends on the situation, or if I am in the winter or I am in the summer, no? If I am in the winter I like to wear jeans, shirt and jacket. If I am in summer, I like jeans and T-shirt or jeans and polo. Classic,” Nadal told Women's Wear Daily in 2013.

Nadal, considered the best clay court player in the world, has won the French Open a record nine times on his way to winning 14 grand slam titles, a total only bettered by his long-time rival, Swiss star Roger Federer.  

His uncle and coach Toni Nadal recently caused a stir when he said Federer was better than his own disciple.

"I think he (Federer) is (the best of all-time), the numbers say that," Toni Nadal told Spanish radio station Cadena Cope.

Federer also eclipses Nadal — just — when it comes to earnings. The Swiss was named the seventh richest athlete in a recent Forbes list while Nadal came in at number nine.