Goran Ivanisevic has been part of Djokovic's training staff for quite a while now but the Croatian left Turin after his son tested positive for COVID-19.
With tennis ongoing and crowds slowly back into the stands, many people tend to forget that the world is still battling a pandemic. Reminders are everywhere and after the son of Goran Ivanisevic contracted the virus the Croatian elected to leave Turin and visit his son. Djokovic brought Ivanisevic with him as he is a valuable asset for the Serbian ever since joining him.
The pair worked together during some of the biggest successes Djokovic had recently and him missing the event will prove a problem. Djokovic won't be on his own though as regular members of his team: Marian Vajda, Marco Panichi, and Ulises Badio are with him. It's unclear whether Ivasenivic will return to the event and whether he would be permitted to come back considering the circumstances.
For now, the Croatian left Turin but he will most likely stay in touch with Djokovic thanks to the wonders of modern technology. Djokovic did not comment on the matter yet.