Back in 2006, Federer claimed Djokovic ‘cheated’ during Switzerland’s Davis Cup clash with Serbia, which the Swiss side won 4-1.
The pair have since intensified their rivalry by battling for all the major honours for well over a decade and they share 34 Grand Slam titles between them.
However, Federer and Djokovic repaired their relationship by teaming up to help Europe win the Laver Cup two weeks ago.
And now Srdjan has slightly changed his opinion of the 20-time Grand Slam winner after watching him in Chicago.
“At the time I said that Federer was a great champion, but a little man. That’s what I am thinking today,” said Srdjan.
“Recently his attitude changed. He is even a coach, you saw him giving him (Novak) suggestions at Laver Cup.”
Following that initial Davis Cup clash 12 years ago, Federer said: “I do not believe at his injuries. I am serious, really. I think it’s not real when he has these injuries.”
Meanwhile, Djokovic opened up about how much he is enjoying being back on top form after a difficult 12 months out injured.
“I mean, look, tennis is a big part of my life. I enjoy the sport,” he said.
“I love this sport. I love competing, travelling, you know, being around people who care about me, who sacrifice their lives for me to be here and most of their time.
“I don’t take that for granted. I understand that many people who are not as fortunate as I am to do what they love to do. To be top of the world in this sport, it’s quite a remarkable, so I always try to remind myself of that.
“Tennis‑wise I’m going to, of course, as long as I have this passion for the sport, keep on going and keep on practising and working and hoping that I can win many big titles and stay No 1.”
Djokovic is back in action at the Shanghai Masters next week as he tries to close the gap on Rafael Nadal’s world No 1 ranking.
However, he will face stiff competition from defending champion Federer.