Sue Barker fears Novak Djokovic may be past his best as the tennis superstar targets an 11th Australian Open crown. And the former British number one claims Andy Murray is proving to be a distraction in his new role as the Serbian's coach.

Former American tennis player Ryan Harrison aimed a dig at Andy Murray during Novak Djokovic’s clash against Tomas Machac on Friday. Murray is currently working as part of Djokovic’s coaching team for the Australian Open after entering retirement following the Paris Olympics.

"I know this court well. I have never managed to win the title here and this man - indicating Djokovic - is the only one responsible. Now I am here to try to sabotage him so that he does not win another Australian Open!" said Murray before telling the story behind the new collaboration.

It will be all business when Andy Murray coaches Novak Djokovic at the Australian Open. While the partnership between two of the biggest rivals in recent men’s tennis history has awakened feelings of shock,

Novak Djokovic and Andy Murray have known each other for a quarter of a century. They played from the age of 12, meeting 36 times as professionals, including 10 Grand Slam matches.

Andy Murray is coaching Novak Djokovic at the Australian Open as the Serbian looks to win the tournament for an 11th time, but there is an issue that awaits the Brit

"Andy Murray over there on the sideline, I think was starting to get a little nervous with what was going on."

John McEnroe feels even Andy Murray was getting nervous for Novak Djokovic during his second-round match at the Australian Open after Jaime Faria took the second set. The 24-time Grand Slam champion has made a habit of being a slow starter at major tournaments in recent years.