“John has been incredible and it is incredible he is in this match,” said seven-time world champion Stephen Hendry. “Last night [in Saturday’s first session] he really struggled for whatever reason.
“Ronnie’s play was outstanding but John seemed really un-Higgins like. Maybe it was a little bit of nerves, a bit of intimidation, but he has just battled to stay in this match. Ronnie did not look the same player.”
After a break of 83 from Higgins in the ninth frame, O’Sullivan won two in a row, thanks to runs of 116 and 80, to hold a dominant five-frame advantage at 8-3.
Higgins won the 12th, but O’Sullivan’s break of 91 left the Englishman 9-4 in front.
But the final three frames were very dramatic. Higgins looked in control of the 14th, with O’Sullivan needing a snooker to have any chance, which he then got, although he could not capitalise.
Higgins took the 15th on a black-ball finish, with O’Sullivan then hitting the table early on in the last frame of the night.
His mood was not improved when he potted a long red but then saw the cue ball follow it into the same pocket, with that foul proving crucial as Higgins took the frame to give himself some hope.
O’Sullivan is fighting to make the Crucible quarter-finals for a 24th time and looking for an eighth world title, which would be a record in the modern era.
He was watched by former Manchester United footballer Paul Scholes during his 10-2 first-round win over Chinese debutant He Guoqiang and, this time, UFC fighter Paddy Pimblett and Liverpool defender Milos Kerkez were in attendance.
They, along with the rest of the crowd at the Crucible, would have left thoroughly entertained.