Ronnie O'Sullivan overcame a dizzy spell to thrash Marco Fu 6-0 and reach the quarter-finals of the Dafabet Masters at Alexandra Palace.

The Chigwell star is seeking an eighth Masters title, and made three century breaks during the opening four frames, with Fu failing to pot a single ball before the interval.

While the 42-year-old defending champion showed compelling form to clinch victory, he said afterwards that he was under the weather.

O'Sullivan said on BBC2: "To be honest with you, I was really struggling. I don't know if I have got a virus or something and I just feel very dizzy.

"I was just playing off instinct. I was thinking, 'Don't stop, just pot balls'. I was really quite struggling and have been like that for the last five or six days.

"I don't feel ill, I just feel dizzy. I think it is maybe a lack of magnesium or something, that is what my nutritionist told me.

"I have been eating well for the last four months, maybe I have overdone the exercise when I have been at home and made myself a bit ill.

"I know I can get through it, I still feel good physically and you just have to do a job."