Djokovic enjoyed a blockbuster 2018 which saw him fight back from injury to reach world No 1.
During a lengthy lay-off from an elbow problem, the Serbian had dropped to as low 22nd in the rankings.
Djokovic won the US Open and Wimbledon this year and now three-time French Open winner Kuerten thinks Federer and Nadal will have to do something special to dethrone him.
“Without any doubt, the biggest message is the one of Djokovic,” Kuerten said.
“He was on a cloud, with all the difficulties you have to get to a very high level. But he returned, and he is the most prepared guy to triumph.
“I believe we ended the year with a guarantee, that in the next three or four years, the big protagonist will be him [Djokovic], and Rafa [Nadal] and Roger [Federer] need to find solutions one more time.
“They are the best for it, but Djokovic is still able to make it. Djokovic now has more room to achieve a complete year having chances to win for a longer time.”
Djokovic’s season finished on a slightly sour note after losing two finals.
He was first beaten by Karen Khachanov in the final of the Paris Masters before being stunned by Alexander Zverev at the ATP World Tour finals.
Nadal had been on course to finish the season as No 1 until he needed surgery on his ankle and pulled out of the competition in London.
Kuerten and the Spaniard are both considered greats of the game on clay and the 42-year-old is backing Nadal to make a big return next season.
“I do not know serious Rafa’s [Nadal] injury is, but he definitely is very willing to fight for the number one,” he added.
“They [Nadal and his team] will choose his key moments in a better way.”
After defeat to Zverev, Djokovic praised the German and insisted that it’s hard to breakthrough in today’s game.
“The new generation of tennis players, they bring a lot of power in their game, especially with the serve,” the Serbian said.
“But I guess it takes them maybe mentally more time to put things together and emotionally than our generation.
“At the same time, you know, Nadal, Federer and I, Andy, I mean, Stan [Wawrinka], this kind of generation has dominated the sport for the last 10 years in terms of Grand Slams, and [Juan Martin] Del Potro, of course.
“It’s definitely not easy for the next generation to break through there.”