Rafael Nadal
Rafael Nadal won the US Open title in 2017JEWEL SAMAD/AFP/Getty Images

Rafael Nadal's uncle Toni Nadal — also his former coach — has said the world number one will find it difficult in 2018 to win as many titles he won this year.

The 56-year-old tactician, who parted ways with his nephew after working with him since the Spaniard's childhood, added the return of Novak Djokovic, Andy Murray and other top stars, who were not at their best in 2017, will make it difficult for his former ward.

Also read: How Djokovic can beat Federer and Nadal in 2018, explains strategy coach

"This year has been it happens that Djokovic has not been at his best and Murray either. And [Stan] Wawrinka, [Kei] Nishikori and [Milos] Raonic have also had problems," Toni, who will now work at his nephew's academy in Mallorca, was quoted by Express as telling Spanish newspaper ABC.

He added: "Next year it will be difficult to win many titles, although I hope Rafael continues to prove he is the best on the clay and win again Monte Carlo, Barcelona and Roland Garros."

Federer, Nadal ruled 2017

Roger Federer

Nadal and his nemesis Roger Federer dominated the rest of the pack in 2017, sharing the four Grand Slam titles between them, much to the surprise of tennis fans. Notably, the two legends had been struggling to win major titles in the last few years as the likes of Djokovic, Murray and Wawrinka were consistently finishing on podiums.

Federer ended his three-year Grand Slam drought at the Australian Open earlier this year, beating Nadal in a fiercely-fought final. He also reigned supreme in the early-season hard court swing, winning a Sunshine double.

The 36-year-old skipped the clay-court season, but came back strong to win Wimbledon -- his 19th Grand Slam title -- in July.

On the other hand, Nadal, who showed promise in the early stages of the season, broke his two-year drought with a historic 10th title at the French Open after winning almost everything on the dirt. He then followed it up with the US Open title and ended the year on top of ATP rankings for the first time since 2013.

Nadal will surpass Federer: Toni

Meanwhile, Uncle Toni has also opined that his nephew will be able to break Federer's Grand Slam record in the coming years.

The 31-year-old, with 16 Grand Slams, is just three major titles behind Federer. Unlike the latter, the Spaniard, fitness permitting, still has quite a few years of tennis left in him.

"I trust that Rafa will last long enough to beat Federer's record," Toni added.