Gareth Copley/Getty Images
The penultimate session of the final belonged to Mark Selby.
Mark Selby 12-11 Ronnie O'Sullivan
Ronnie O'Sullivan took the initiative right from the off in the first frame of the afternoon. 10-7 up overnight, you sensed that the defending champion wanted to get things over with as quickly as possible.
A lack of concentration saw him down the cue ball and Mark Selby took full advantage, a break of 55 taking him back to within two frames.
At 73-22 up in the second, Selby needed just a red to leave O'Sullivan with snookers, but a missed pot let the latter back in. Fortunately for Selby, O'Sullivan couldn't take advantage. The five-frame advantage O'Sullivan held from the previous evening was gently but very definitely being eroded by Selby.
The confidence of the "Jester from Leicester" was clearly sky high as he strode confidently around the table and a well-built break of 74 took him level, and the Crucible erupted as he took the last frame before the mid-session break.
During live commentary, BBC TV's John Parrot noted:
If you're Ronnie O'Sullivan what do you do [...] since the first frame he's been outplayed. Every time he comes to the table he's been outplayed [...] there's always a problem, something to solve, lots of snookers.
Things were that bad for the "Rocket" that a sports psychiatrist was summonsed to his dressing room where he stayed throughout the mid-session break.
Both players suffered unbelievably from nerves in the first frame back, missing colour after colour. Even the simplest of pots seemed beyond them.
Selby took the chance to go ahead and things began to look anonymous for O'Sullivan. In a sign of his character a 50 break saw O'Sullivan draw level, taking the frame 76-38.
At 11 frames apiece, the tournament director took the decision in the middle of the next frame to make it the last, and give the player a rest before the final evening session.
It ended up being the longest frame of the day as the advantage swung back and forth, both players careful with their safety shots. At 58-57 to O'Sullivan, it looked for all the world as if the defending champion would go into the final session ahead.
A missed pink astonished the entire crowd and the commentary team who noted "even a pub player could've potted it. Unbelievable."
It allowed Selby the chance to nick the frame on a very difficult black and go into the final session ahead.
Only one frame in the afternoon for O'Sullivan really puts him under pressure for the evening session. Where O'Sullivan looks erratic, Selby by contrast has looked confident and assured.
It will be the first time O'Sullivan has gone into the final session at the Crucible behind. Only four people in the Crucible's illustrious history have managed to win the title from that position.