The king is dead. Long live the king. As Rory McIlroy's bid for a hat-trick of titles ended in tears and frustration in the Radisson-SAS West of Ireland Championship, his teenage contemporary from nearby Strandhill, Tommy McGowan, appeared on the scene as the heir apparent.

An almost unbackable favourite with the resident Rosses Point bookmaker, defending champion McIlroy made his exit in the quarter-finals when he was beaten by one hole by Irish Boys international Paul Cutler from Portstewart.

But the huge crowds that turned up at County Sligo Golf Club didn't seem to mind at all as 17-year-old McGowan, a fifth year student at Summerhill College in Sligo, confounded the odds by making it to the last four thanks to a brace of victories on the 18th green.

Out of sorts with his putting all week, McIlroy had still cruised into the last eight with a 4 and 3 win over Rory Leonard of Banbridge in his morning match, but he paid the ultimate price for an erratic putting display against 18-year-old Cutler.

Birdies at the first two holes put the reigning European Individual champion two up. But what looked like the start of another imperious victory march turned into a messy scrap from the moment McIlroy went out of bounds at the sixth, and then lost the eighth to a birdie to be pegged back to all square.

He then three-putted the ninth to fall behind, and while he won the 11th, 12th and 13th to restore his two-hole cushion, he was disgusted to lose the 14th and 15th to pars and even more upset when he failed to match Cutler's superb pitch and putt birdie at the last.

Left with an eight-footer to force extra holes, McIlroy pulled his putt wide of the target and said goodbye to Rosses Point for the last time, as he prepares to turn professional after September's Walker Cup.

"I didn't putt my best this week," said a visibly upset McIlroy. "I didn't hole the putts that I usually do and that was the big difference. I am really disappointed. This was the one I really wanted to win and I didn't do it.

"I already have a win this year in the Sherry Cup, so I shouldn't be hard on myself. I just tried really hard this week to win three in a row, but obviously I couldn't do it."

Cutler was delighted to pull off a victory he described as "unbelievable", but he will face a serious challenge against local hero McGowan in this morning's semi-finals.

The Strandhill player got into the championship thanks only to an exemption from the Connacht Branch, but he is determined to ride his wave of support as long as possible and become the first Sligo man to take the title since Cecil Ewing in 1950.

A 20-foot birdie gave him a one-hole victory over Lee Valley's Niall Gorey in the morning, before he closed out another one-hole victory over Lancashire's Jonathan Hurst.

The key to that one came at Rosses Point's fearsome 17th, where McGowan rifled a 197-yard four-iron to six feet and rolled in the putt to roars of "Come on Tommy boy" to take a one-hole lead.

Hurst lipped out with an effort at the last that would have forced extra holes.

"To be honest, it hasn't hit me yet," McGowan said. "I am just coasting along, taking it one game at a time. I don't think I even realised I was playing in the semi-finals. I was floating along playing on front of those crowds. I don't think I was too aware of what I was doing, to be honest."

With McIlroy making his exit, leading qualifier Simon Ward from Co Louth is now the championship favourite following his two-hole win over Richard Kilpatrick of Banbridge.

But the 20-year-old South of Ireland champion will need to be at his best to see off 34-year-old Joe Lyons this morning after the Galway player racked up seven birdies and didn't drop a shot in an impressive 7 and 6 win over Newlands' Andrew Hogan.

"He stitched everything," said a shell-shocked Hogan, who was level par on his card. "It was unbelievable stuff."