Injury puts Colin Montgomerie out of Irish Open
Last year's Ryder Cup captain was to have lined up alongside Ireland's four major winners Padraig Harrington, Graeme McDowell, reigning US Open champion Rory McIlroy and new Open champion Darren Clarke.
Montgomerie has not played since the Scottish Open three weeks ago, failing to qualify for The Open after sharing the lead at Castle Stuart early in the final round.
He has also not made the field for next week's WGC-Bridgestone Invitational in Akron or the final major of the year, the US PGA Championship in Atlanta starting on 11 August, so his next appearance might not be until the Czech Open a week later or the Johnnie Walker Championship at Gleneagles at the end of next month.
Open champion Clarke will play in his first tournament since winning The Open at Sandwich earlier this month.
He will be joined at Portmarnock by fellow major winners McDowell and McIlroy in what should prove to be a celebration of golf in Northern Ireland, with Clarke saying that the scenes "could be like nothing we've seen before".