Djokovic returned to the sport this month and has got through week one of the first Grand Slam of the year.

He dispatched Donald Young, Gael Monfils and Albert Ramos to get into the fourth round.

Chung Hyeon is the man in the way of a quarter-final spot.

But Rusedski admits he’s already been surprised with how well Djokovic has done in his first Slam back after a lengthy injury.

“I think he’s played great,” Djokovic said on Eurosport.

“I was very surprised. I predicted he’d go out in the second round. I didn’t think he had enough matches in him.

“I was worried about he serve with the abbreviated motion. He’s going to have aches and pains. Let’s not forget Roger Federer when he won here last year he had a little problem with his back a few times so Novak’s going through the same thing. 

“But he’s been winning so I’ve been very impressed with him so far.”

Djokovic admitted he was struggling with his fitness over the weekend and that he still wasn’t at 100% following his lay off when he cut his season short last year.

He said: “I am still not 100% but I’m getting there and it feels like every match I’m getting into the groove more and I feel like I’m playing better and feeling more comfortable. 

“One thing is to play practice sets before the tournaments but it’s another thing to play here with he crowd, pressure, nerves kick in. 

“I take it day by day obviously and then I face a little bit of physical difficulties with my hip. It’s ok now thankfully it’s just one of these things that surfaces after a long time of not competing. It was the first time for me thats what it was surprising.”