BBC Sport t Russell Fuller looks at the key questions after a players' union co-founded by Novak Djokovic began legal action against tennis' governing bodies.

The tennis players' association co-founded by Novak Djokovic has sued the main groups that run the sport in a bid to gain more money and control.

The tennis players’ association that was co-founded by Novak Djokovic has filed multiple lawsuits around the world against the sport’s tours and governing bodies.