Shane O'Neill's side, famously beaten here by Loughgiel Shamrocks in the semi-finals six years ago, trailed the back to back Ulster champions by three at half-time.

They were then reduced to 13 players when goalscorer Conor Boylan and defender Tommy Grimes were both dismissed within minutes of the restart for separate striking offences.

But they conjured their best form from there and second-half goals from Limerick duo Kevin Downes and Shane Dowling helped seal a surprisingly comfortable win in the end.

Ronan Lynch, another county man, top scored with 14 points, 11 from placed balls, in a five-star display and won the Man of the Match award, marginally beating full-back Mike Casey to the gong.

Na Piarsaigh advance now to next month's All-Ireland decider at Parnell Park and will play holders Cuala or Liam Mellows.

Slaughtneil, Ulster senior club champions in both codes, arrived at the Donneycarney venue armed with a vocal support base who roared in approval as they controlled the first-half.

Captain Christopher McKaigue opened the scoring after two minutes and, save for a couple of periods when the sides were level, Slaughtneil remained in pole position for the most part.

Cormac O'Doherty fired two points before nailing a 16th minute goal for Slaughtneil from a penalty that put clear daylight between the teams.

The influential Brendan Rodgers was hauled down by full-back Casey and O'Doherty slammed the resulting penalty to the roof of the net.

Boylan responded with a Na Piarsaigh goal six minutes later when he shot home under pressure from the left, levelling it at 1-4 apiece.

But the Slaughtneil response was emphatic, and indicative of their enthusiastic approach all afternoon, as they reeled off 1-1 in the following 90 seconds.

Meehaul McGrath thundered over a point shortly after Boylan's net blast before Rodgers this time set up Brian Cassidy for a goal with a great catch.

Slaughtneil deservedly led by 2-6 to 0-6 at half-time and were making a mockery of the 11-point handicap placed on Na Piarsaigh by bookmakers.

But they were remarkably reduced to 13 men by the 35th minute following the dismissals of goalscorer Boylan and wing-back Grimes, both for striking offences.

That left Slaughtneil with the greater numbers but Na Piarsaigh, apparently sparked into life by the losses, stormed clear on the scoreboard.

Lynch converted a succession of frees before Dowling fed Downes for a 41st minute goal that put Na Piarsaigh 2-11 to 2-6 clear.

Rodgers and Cassidy pulled back Slaughtneil points to reduce the deficit to three but they only scored once more in the game, a consolation Gerald Bradley goal with a minute of normal time remaining.

Na Piarsaigh, in contrast, continued to pick off the points and with their defence superb had a strong platform to remain on top of an overwhelmed Slaughtneil who failed to bring their two extra players to bear on the game.

Na Piarsaigh scorers: R. Lynch 0-14 (0-11f), S. Dowling 1-0, K. Downes 1-0, Conor Boylan 1-0, Peter Casey 0-1.

Slaughtneil scorers: C. O'Doherty 1-3 (1-0 pen, 0-2f), B. Cassidy 1-2, G. Bradley 1-0, B. Rodgers 0-1, C. McKaigue 0-1, M. McGrath 0-1.

Na Piarsaigh: P. Kennedy; N. Buckley, M. Casey, J. Boylan; A. Dempsey, C. King (c), T. Grimes; R. Lynch, W. O'Donoghue; C. Boylan, D. Breen, D. Dempsey; P. Casey, K. Downes, A. Breen.

Subs: K. Kennedy for Grimes (24-25, blood); S. Dowling for A. Breen (h/t); K. Ryan for D. Breen (55); Kennedy for D. Dempsey (56); G. Brown for Downes (60).

Slaughtneil: O. O'Doherty; K. McKaigue, S. Cassidy, P. McNeill; S. McGuigan, C. McKaigue (c), C. McKenna; E. Cassidy, M. McGrath; B. Rodgers, C. O'Doherty, M. McGuigan; G. Bradley, B. Cassidy, C. McAllister.

Subs: G. O'Kane for McAllister (49).

Ref: J. Keenan (Wicklow).