That’s the view of former Swiss player and close friend of Roger Federer, Yves Allegro.
Djokovic is entering arguably the biggest few months of his career as he aims to rewrite the history books.
At the French Open, which begins in May, the Serbian can win a fourth successive Grand Slam title.
It would mean the 31-year-old was the holder of all four Majors for the second time in his career and the first man to accomplish the feat.
But when asked if Djokovic was favourite for the French Open, Allegro told Swiss outlet Bluewin: “No, for me [Rafael] Nadal remains the favourite.
“It is always dangerous to make a prognosis. When we thought that Federer would win everything, he started to lose.
“We thought that Roger would not win a Grand Slam title anymore, since then he has won three.
“Also Nadal had already been written off and shortly thereafter he was in the final of the Australian Open.
“At Djokovic we thought he would win 25 Grand Slam titles and suddenly there was nothing left.
“So many things can happen that predictions are really difficult.
“But yes, I think that Djokovic will end the year as number one in the world.”
Speaking at the Miami Open last week, Federer said the idea of becoming world No 1 again would be a joke.
“I think it’s not reasonable to think that way at 37,” said Federer.
“I think it was one of the favourite moments in my life last year in Rotterdam when I was able to get back to world number one at 36, having won the Australian Open and Wimbledon in the same year, and winning the Sunshine Double and all that stuff, it just aligned itself beautifully.
“Novak has just won three (Grand) Slams, so I think it would be a bit of a joke if I said that was my goal.”