‘He takes your soul’: Novak Djokovic responds after being labeled ‘beast’ as roars back to beat US youngster in New York (VIDEO)

Former tennis world number one and 2003 US Open champion Andy Roddick has fired off tweets about the game's modern-day ruler Novak Djokovic, claiming he takes opponent's legs and soul, with the Serb replying with humor.

As the last Grand Slam of the year progresses at Flushing Meadows, Djokovic faced world number 99 Jenson Brooskby and received an early scare from the 20-year-old.

As the American took the first set 6-1, Roddick praised him for being "so, so good" and "tough", while tagging his wife Brooklyn Decker and declaring that "I think that I love another" after apologizing.

"No apologies necessary sweetheart, please go back on tour," the model demanded of her husband, who has been retired since 2012.

Yet the early developments proved to be a false dawn for Brooskby, who allowed Djokovic to come back into the match and clinch the following three sets for a 1-6 6-3 6-2 6-2 win.

The comeback was something that Roddick - the last American male to win a Grand Slam - had predicted.

"I promise you one thing," he wrote.

"As we get into this, Novak will make this the most painful physical experience this kid has ever seen. Hour and a half in, and some serious body blows thrown. We know Novak can handle it……."

Quoting his own tweet as the tide turned, Roddick said: "An hour ago. We’ve seen this before …. Novak’s fitness used to be a weakness. One of the best examples in sports history of turning a negative into a positive. He’s a beast."

"First he takes your legs ……. Then he takes your soul," he chillingly added.

Alerted of this in his post-match interview as he celebrated passage to the quarter-finals, Djokovic let off a big grin with the crowd laughing and replied: "Thanks Andy, I take that as a compliment." 

"Only the first part [is true], the second part - I don't take anybody's soul. Everyone has their soul, we are all beautiful souls, so I appreciate everyone," he insisted.

Asked to comment on his game foe, who came racing out of the tracks early doors, Djokovic said Brooksby "just played a perfect first set" and is "very clever".

"I couldn't do anything. He played a perfect first set. Everything he intended to do he executed it perfectly," Djokovic explained.

"On my end, I was just trying to find a rhythm, trying to read his game, trying to understand where I can find holes in his game and start to attack and shift the momentum to my side."

"I really wanted him to feel my presence on the court. I wanted the energy to shift to my side because he was a better player for a set and a half. He had the momentum.

"I felt like that was the point where, okay, now I've got him. He also was struggling a little bit physically at one point. I wanted to wear him down and it worked," he concluded.

As for Matteo Berrettini, who he will face tomorrow in a repeat of this year's Wimbledon final which Djokovic won, the veteran reminded us that the Italian is the "hammer of tennis".

"Next to [Juan Martin] del Potro, [he's] probably the hardest hitter of the serve and forehand. He's got the lethal serve-plus-one game. He's already established as a top player," said Djokovic.

"Without a doubt, he played a semi-final here a couple years ago, the final in Wimbledon. That was a tough four-setter. If he serves well, which is his biggest weapon, he's tough. He's tough on any surface to play against."

"I've had some really close matches with him at [Roland Garros] and Wimbledon recently. We're going to play the third Grand Slam in a row against each other. Hopefully the result will be the same as the previous two," Djokovic signed off.