Ailing O'Sullivan struggles through
Ronnie O'Sullivan revealed he is struggling with a virus after coming close to a shock first-round loss at the Dafabet Masters at Alexandra Palace in London, eventually beating China's Liang Wenbo 6-5.
Ulsterman Mark Allen is in action today against John Higgins.
Defending champion O'Sullivan was 5-4 down as Liang won three straight frames to overturn a 4-2 deficit.
And the best-of-11 contest reached the decisive frame, when O'Sullivan recorded his best break, of 121.
The 41-year-old Englishman, a five-time world champion, is seeking a record seventh Masters title.
"You've got to feel for Liang," admitted world number 13 O'Sullivan. "He should have won that match. He should have put me away.
"I don't think I was much of a fight throughout the whole match, I just managed to nick a few frames through my experience. Maybe that was the difference. I didn't feel very good in myself. I've had a bit of a virus. I just felt really lethargic, really tired.
"Hopefully in the next couple of days I can shake off this bug and feel better."
O'Sullivan will play either Neil Robertson or Ali Carter in the quarter-finals.
The tournament finishes next Sunday.