Ronnie O'Sullivan and Gary Wilson are locked together at 4-4 after the opening session of their Tour Championship semi-final in Manchester.
Wilson rallied brilliantly from 4-2 down to win the final two frames of the afternoon with breaks of 83 and 84, but was left frustrated after a controversial moment in frame six cost him what might yet prove a match-defining frame.
After O'Sullivan broke down on 53, Wilson looked sure to produce a successful counter attack, only for referee Paul Collier to call a foul when Wilson potted the red, believing the cue ball had made contact with adjacent pink beforehand.
Replays appeared to confirm that the pot was clean, but despite Wilson's protestations, Collier was unperturbed and O'Sullivan gratefully took his chance to win what was his fourth frame on the bounce.
O'Sullivan had looked close to his peerless best at that stage, a pair of centuries maintaining the level of form that saw him cruise past Ali Carter in the previous round, and that moment of controversy only deepened Wilson's frustrations.
It was a far cry from the opening throes of the afternoon when Wilson dominated the first two frames to lead 2-0, and he will be relieved to have gathered himself admirably in the last two frames to leave the contest all square.
The match will resume this evening at 7pm.
