Irish champion Paul O'Hanlon produced a magical putting display to end Eddie Power's South of Ireland hopes at storm-lashed Lahinch.
The man from the Curragh, 23, was forced into extra holes when Kilkenny veteran Power got up and down from 40 yards for a winning par at the 18th.
With rain and wind lashing the Clare links, O'Hanlon holed a 15 footer to stay alive at the 19th and another 15 footer at the 20th, where Power dashed into the clubhouse to replace a lost contact lens.
But it all ended at the third tie hole when he drained another 15 footer for a winning par that set up a semi-final clash with Lee Valley's Niall Gorey today
Kildare native Gorey, 28, had never been past the last 16 in any championship before he ended Shane Lowry’s bid of a hat-trick of provincial titles with a 3 and 2 fifth round win.
Now operating Ballincollig Golf Centre in Cork, he moved into uncharted territory with a 2 and 1 quarter-final win over Athlone teenager Kelan McDonagh and he believes he is ready to step up a level now that his new job gives him more time to practice.
Gorey said: “It was a bit of a birdie-fest against Shane but this afternoon just required experience. I was a bit nervy in the first couple of holes but once I got ahead the objective was to keep it that way and not even let him get to all square.
“I haven’t been behind in any of my matches and my objective all week has been to get ahead and stay ahead and not make any stupid mistakes.
"Before I moved to Cork I was away two or three nights a week with my job and I wasn’t able to compete against the young kids. A couple of years ago, if I had played a guy like Shane, I would have had no chance."
A winner of five points out of five in last year's Interprovincial matches, Gorey knows that a Championship victory would pave the way to international honours.
But he refused to get ahead of himself, explaining: "I am not here to get a cap. Like everyone else, I have come here to win. Simple as that.”
A fourth year student at South Eastern Lousiana, Douglas ace Aaron O'Callaghan, 22, will take on Royal Dublin international Niall Kearney in the second semi-final after a 12-hour day at the Co Clare links.
And he paid tribute to Munster coach Fred Twomey, who helped him remodel his swing last November to better adapt to the power game he needs to succeed in college golf in the US.
Resuming his weather delayed fourth round clash with Ballybunion's John D Guiney on the 13th tee at 7 am, he closed out a 4 and 2 win before hammering Cork's Fergal Deasy 6 and 5.
But it was a war of attrition against Californian teenager Austin Graham, 18, in the wind and rain lashed afternoon quarter-finals, where he eventually came through to win by one hole.
He said: "I have played awful in the US for the last 12 months but the last couple of weeks it has started to come together. Today it was a grind but I have been ripping it all week."
Kearney, 20, came back from two down after nine holes to beat Knock's Nicky Grant 2 and 1 and hopes to go on and earn his first senior championship title.
Now a full-time amateur, he said: "The best I have played this year was in the Brabazon Trophy, where I was sixth. I used to think I was better in strokeplay but I think I am a better match player now than I used to be."
South of Ireland Amateur Open Championship
Fourth round (carried over from Mon):
E Haugh (Castletroy) bt G Dunne (Seapoint) 3/2;
S Ward (Co Louth) bt R McNamara (Headfort) 4/3;
A Graham (Pacific G&CC) bt D McInerney (Lahinch) 2/1;
A O'Callaghan (Douglas) bt JD Guiney (Baybunion) 4/2;
F Deasy (Cork) bt T Neenan (Lahinch) 3/2.
K McDonagh (Athlone/NUIM) bt P Murray (Limerick) 1 hole;
N Gorey (Lee Valley) bt S Lowry (Esker Hills) 3/2;
E Power (Kilkenny) bt K Canty (Douglas) 6/5;
P O'Hanlon (The Curragh) bt A Hogan (Newlands) 3/2;
N Grant (Knock) bt A Condren (Greystones) 3/2;
N Kearney (Royal Dublin) bt E Haugh (Castletroy) 6/5;
A Graham (Pacific G&CC) bt S Ward (Co Louth) 1 hole;
A O'Callaghan (Douglas) bt F Deasy (Cork) 6/5.
N Gorey bt K McDonagh 2/1;
P O'Hanlon bt E Power 21st;
N Kearney bt N Grant 2/1;
A O'Callaghan bt A Graham 1 hole.
(8.30) N Gorey v P O'Hanlon;
(9.00) N Kearney v A O'Callaghan.