Irish Close champion Shane Lowry beat the Castle's Ryan Boal at the 20th to clinch his place in Wednesday's West of Ireland Championship semi-finals at Rosses Point.
The 20-year-old from Esker Hills birdied the 18th from 30 feet to force extra holes before taking the match with a par-four at the second tie hole after Boal three-putted.
Lowry, 20, will face 35-year-old Eddie McCormack from Galway GC after the Cavan native beat Michael Lavelle of the K Club 4 and 3.
The Curragh's Paul O'Hanlon, who was a beaten finalist in 2006, will face Mullingar's Dessie Morgan in the other semi-final.
O'Hanlon came from behind to beat England's Jonathan Hurst 2 and 1 while Morgan had a clear cut 3 and 2 win over Knock's Michael SInclair.
Radisson SAS West of Ireland Championship, County Sligo GC
E McCormack (Galway) bt J Fox (Portmarnock) 1 hole;
M Lavelle (K Club) bt A McCloy (Ballymena) 4/3;
R Boal (Castle) bt J Monaghan (The Island) 3/2;
S Lowry (Esker Hills) bt B Cashman (Belvoir Park) 7/5;
J Hurst (Shawhill, UK) bt G McDermott (Co. Sligo) 1 hole;
P O’Hanlon (Curragh) bt A Hogan (Newlands) 4/3;
M Sinclair (Knock) bt P Cutler (Portstewart) 4/3;
D Morgan (Mullingar) bt D Downie (Sutton) 3/2.
Quarter-finals: E McCormack bt M Lavelle 4/3; S Lowry bt R Boal 20th; P O’Hanlon bt J Hurst 2/1; D Morgan bt M Sinclair 3/2.
Semi-finals: (8.00) McCormack v Lowry; (8.15) O’Hanlon v Morgan.