In recent years the Ballon d'Or award has been rotated between Real Madrid's Cristiano Ronaldo and Lionel Messi of Barcelona.
Messi has scored over 500 goals for Barcelona, while Ronaldo has netted over 400 times for Real. The 26-year-old Hazard, who is currently out of action with an ankle injury, has scored 122 goals for the clubs he has played for
-- Chelsea and Lille -- as well as 17 times for Belgium.
"I think he has the capacity to win it because, for me, he is a very talented player, a very good player, a decisive player," Nainggolan, who plays for Italian side Roma, told CNN Sport as he reflected on Hazard's talents.
"He makes a difference on the pitch, but the only difference between him and, let's say, Neymar, Cristiano Ronaldo and Messi, is that they score much more than him."
"So, I think that is the most important thing and it's the only difference between them, because for me Hazard is, let's say, is in world's top five," added Nainggolan, who was speaking to CNN during Roma's preseason tour in the US.
Hazard reportedly returned to training with Chelsea earlier this week after fracturing his ankle on international duty with Belgium in June.
'It's not only about money'
Meanwhile, Nainggolan -- who has often been linked with a move to the English Premier League -- says he's very happy at Roma.
"It's not only about money," said the midfielder, who joined Roma in 2014.
"I have a lot of ambition, but I think you have to be happy and that you have to live well.
"My family is living well, I'm happy where I am playing, so now I'm 29 and I had to think about what to do and I think about the best thing and the right thing for me and my family, which was staying in Roma."