By Lou Aguila (staff@latinospost.com) | First Posted: Aug 01, 2013 01:28 PM EDT

Srdjan Djokovic, the father of world's No. 1 Novak Djokovic, put himself at the center of controversy recently after firing verbal jabs at Roger Federer and Rafael Nadal.

In an interview with Serbian newspaper Kurir, the elder Djokovic launched a full-on attack against Federer and Nadal, the two best tennis players of the last decade, as he questioned their sportsmanship and even credibility as men.

"Federer is perhaps still the best tennis player in history, but as a man, he's the opposite," Srdjan said of Federer, who hasn't had a close relationship with Novak's family throughout the years of playing each other.

Five years ago, Federer made a rare gesture towards Djokovic's family after calling for them to be quiet in the semifinal of the 2008 Monte Carlo Masters.

Earlier that year, Djokovic's mother Dijana made an eyebrow-raising comment following her son's victory over Federer at the Australian Open, saying the "King is Dead."

But the statement Novak's father hasn't forgotten was when Federer criticized Djokovic's injury during a Davis Cup duel in Geneva in 2006.

"He attacked Novak at the Davis Cup in Geneva [in 2006], he realized that he was his successor and was trying to discredit him in every way. Novak's success is an amazing thing and something that one cannot understand," Srdjan added.

Novak's father didn't stop there. He shifted his verbal barrage to Nadal, stressing that the Mallorcan's relationship with Djokovic had suddenly cooled down when his son started beating him.

"Nadal was his best friend while he was winning. When things changed, they were no longer friends. This is not sport. This is what Novak has in him, but others don't," he said.

Meanwhile, Srdjan had words of appreciation for Novak's current adversary Andy Murray and his family, calling the Brit a "correct" rival.

"They cannot be best friends as they fight for the most important titles, and lots of money. But they are more than correct rivals and I am sure that after they finish their professional careers, they will be great friends," Novak's father added.

Djokovic, Murray, Nadal, and Federer have shared several intense moments playing one another over the past five or six years, and the tension is expected to escalate even more next month when the tennis season shifts to hard-court play.