Djokovic brought Croatia's 2001 Wimbledon champion on board as a member of his team ahead of the grass court Grand Slam in 2019 and under his guidance won 12 of his 24 career major titles.
"Concerning my following stage about a coach for me I don't have any clear idea who that might be and if anyone will be," Djokovic said at a press conference in Belgrade.
"I have always had coaches by my side, since I was young. I am trying to feel what is good for me in this moment."
Djokovic has had a poor start to the year by his standards, losing to eventual champion Jannik Sinner in the Australian Open semi-finals. The 36-year-old then lost to Sinner's unheralded compatriot Luca Nardi in the third round at Indian Wells, prompting him to withdraw from the ongoing Miami Open.
He is due to return to the tour at the Monte Carlo Masters next month in the build-up to the season's second Grand Slam of the year at the French Open.
