Mark Selby won six of the last seven frames to beat Kyren Wilson 6-5 and set up a Champion of Champions semi-final clash with Neil Robertson.
The three-time World Champion had trailed 4-0 to the Kettering potter at the mid-session interval of their Group 4 final at Marshall Arena, Milton Keynes. But he dug in and began the fightback after the break, winning the next three frames.
Wilson moved to within one of the semis at 5-3, but Selby kept on fighting to force the decider, which he won with a break of 74 to reach his first Champion of Champions semi final since 2013.
World champion O’Sullivan begins his campaign against Michael Holt on Thursday afternoon at 1pm (GMT) with Mark Allen facing Scott Donaldson in the other Group Four contest.