Nick Kyrgios admits he has not fully committed to his career since the death of his grandmother two years ago.
The Australian, ranked 20th in the world, said: "I didn't get to spend the time with her I wanted to and tennis was the reason for that. It kept me away from her. It's something that still gnaws away at me.
"If I'm honest, I'd say I haven't committed to tennis the way the game needs me to since she died."