Six-time World Championship runner-up Jimmy White says he "strongly believes" he can still win the title.
White, 52, has not reached the Crucible final since 1994 and has failed to qualify for the event since losing in the first round in 2006.
But he told BBC Radio 5 live: "I'm not finished yet. My eyes are good, I'm still playing good.
"Make no mistake, I'm really knocking on the door. I still have very strong belief that I can win it."
White confessed in his recent autobiography to using cocaine regularly at the height of his career.
"I didn't prepare right before," White told 5 live. "Of course [it stopped me winning things]. I was the biggest mug in the world."
White is currently ranked 62 in the world and concedes it will be tough to realise his Crucible ambitions.
"The modern sport now, you've got so many good players," he said. "They're all regimental, they all practise six or seven hours a day.
"But I'm playing as good as ever. I wouldn't play [if I didn't think I could win]."