Murray, who recently agreed to coach Djokovic into and through the Australian Open, left a comment questioning the Serb's decision to take time out of his practice schedule.

"He should be on the practice court," joked Murray. Djokovic instantly apologised with his reply, which read: "Sorry coach, I will be back soon," alongside a laughing emoji.

He will be hoping that his partnership with Murray is a fruitful one, with the 37-year-old hoping to end his Grand Slam drought by claiming the top prize at the Australian Open in January.

While in Qatar, Djokovic gave an interview to Sky Sports explaining why he felt he had made the perfect decision by appointing Murray as his new coach.

"We were going through different names and I realised the perfect coach for me at this point would be someone that has been through the experiences that I’m going through," he said.

"I was thinking about different people and then an Andy Murray discussion appeared on the table with me and my team. It was still a shock decision. It caught him a little bit off guard as well because he wasn’t expecting it.

"We connected really fast and he accepted after a few days. I couldn’t be more excited about it. This collaboration is a surprise to me as well, to everyone, but it’s exciting for tennis.

"He’s been one of my greatest rivals. We’re the same age. We’ve played in all the biggest stadiums in our sport, so I can’t wait to get out on the court and prepare for next season."