The seven-time champion took control of the quarter-final on Tuesday as he moved into a 6-2 lead, leaving him seven frames away from victory.
O’Sullivan is competing in his first competitive tournament since January and the 49-year-old has been keen to lower expectations, insisting he is “nowhere near” his best and that his current level is not good enough to win the tournament.
It has been relatively serene progress up to this point, though, and O’Sullivan is a big favourite to reach the semi-finals and keep his bid for a record-breaking eighth title alive at the Crucible.
“I don’t mind who I play as long as I play my game,” O’Sullivan said. “It’s irrelevant who is sitting in the chair, I always back myself if I can play somewhere near my best level.
“I’m not sure I’m close to that but it can click at any time.”
The winner of this match is likely to face Zhao Xintong next, after the 28-year-old from China raced into a 12-4 lead over Chris Wakelin.
What time is O’Sullivan vs Si?
The match will resume this morning at 10am BST, when eight frames will be played. If another sessions is required, O’Sullivan and Si will play to a conclusion this evening, with the action getting underway again at 7pm.
TV channel: In the UK, the World Snooker Championship is being broadcast live and free-to-air across the BBC. Coverage of the morning session today begins on BBC Two at 10am.
Live stream: O’Sullivan vs Si will be shown in full online via BBC iPlayer and the BBC Sport website.
