"I am no longer working with Wu," Sven Groeneveld wrote on Twitter. "He has a right to have a coach whose views are better aligned with his mother."
Defending champion Roger Federer, world number two Angelique Kerber and five-time Grand Slam winner Maria Sharapova were all crashed out of the Australian Open.
Gutsy Andy Murray fought to the end before losing an epic farewell match at the hands of Roberto Bautista Agut. But it was business as usual for ruthless Roger Federer and Rafael Nadal, who joined Caroline Wozniacki in round two.
Simona Halep fought back from a set and a break down to finally achieve her "dream" of winning a Grand Slam title, beating Sloane Stephens 3-6, 6-4, 6-1 in a gruelling French Open final on Saturday.
Serbian star Djokovic had little trouble in reaching round two, though, seeing off Brazilian world number 134 Rogerio Dutra Silva 6-3, 6-4, 6-4.
While Nadal dropped a set to win the mens titles, Elina Svitolina defended the women's title, scorching through to her title in a mere 67 minutes.
Nadal and Djokovic have played each other 50 times, but their last meeting came more than a year ago, when Nadal won in the Madrid Open semifinals. Djokovic leads Nadal 26-24 overall, but Nadal holds a 13-7 advantage on clay.
The former world number one Maria Sharapova loses first round match with a 6-4 6-4 defeat to Japan's Naomi Osaka at the Indian Wells tennis tournament.
Russia's Alexander Krushelnitsky, who competes in curling, one of the Games' least physically taxing sports, is suspected of testing positive for Meldonium – the same substance that saw Russian tennis star Maria Sharapova suspended.
Meldonium burst to the fore in 2016 when Maria Sharapova announced that she had failed a drugs test. Although she was banned for 15 months, more than 170 athletes have since tested positive for the substance, Olympians included.
Alexander Krushelnitsky still has to be officially named and undergo a second test, but if confirmed the incident could keep the Russia's banned team from being reinstated and marching under the national flag at the closing ceremony.
Federer continued his dominance over Richard Gasquet to reach the round of 16 at the Australian Open and keep his quest for a 20th Grand Slam title on track.
Subscribe to our Youtube channel for all latest in-depth, on the ground reporting from around the world.
Copyright © 2019 TRT World.