Listed at number 14 on the programme, but held in reserve, the introduction of wily veteran Darragh Holland proved to be the match-winning move.
Holland hit a glorious point to leave just the bare minimum between the sides with time running out and then pounced to score the winning goal in injury time after receiving from outstanding wing back John Olden.
It was a sweet victory for Inniscarra but a cruel defeat for Youghal who were reduced to 14-men midway through the second half when corner back Alan Geary was sent off after receiving a second yellow card.
Brendan Ring pointed Youghal into an early lead. And with wing forward Leigh Desmond turning on the style, the seasiders threatened ominously to crush their opponents.
The accurate Desmond hit six points in succession, four from frees, as Youghal powered their way into an interval lead of 0-7 to 0-4.
Youghal resumed with two lightning fast points from Desmond and Brendan Ring and when they established a six points lead in the 38th minute it looked all over for Inniscarra.
But following Geary’ dismissal in the 44th minute, the tide turned and Inniscarra grew in the ascendancy.
O’Regan hit some superb points as did John Olden and Holland as Inniscarra thundered back into contention. It was exciting stuff now as Inniscarra came within range but a magnificent point from centre back Brendan Coleman seemed to have secured it for Youghal.
That was until Holland intervened.
Scorers for Inniscarra: D. Holland 1-1; N. O’Regan 0-6 (0-3 from frees); D. O’Connell 0-2; J. Olden, S. Olden and A. O’Mahony (sideline cut) 0-1 each.
Youghal: L. Desmond 0-8 (0-5 from frees); B. Ring 0-2; B. Coleman and E. Coleman 0-1 each.
INNISCARRA: P. O’Sullivan; D. O’Mahony, G. Burke, C. Holland; K. Dineen, J. O’Mahony, J. Olden; L. O’Riain, J. O’Callaghan; J. Cully, S. Olden, J. Casey; N. O’Regan, A. O’Mahony, D. O’Connell.
Substitutes: D. Holland for S. Olden; B. O’Keeffe for C. Holland.
YOUGHAL: R. Cunningham; M. O’Brien, V. Murray, P. O’Laochdha; S. Twomey, B. Coleman, D. Ring; G. Geary, K. Walsh; L. Desmond, E. Coleman, B. Ring; S. Kenneally, A. Murphy, N. Roche. Substitutes. A. Geary for O’Brien (leg injury); C. O’Laochdha for G. Geary.
Referee: P. O’Neill (Shamrocks).