Darren Clarke's Open Championship victory was not enough to get him into Ireland's two-man team for the World Cup in China in November.
World number four Rory McIlroy had the right to invite Clarke, Graeme McDowell or Padraig Harrington to be his partner and he opted for McDowell.
"G-Mac's the next highest on the rankings, so it will be me and him again," said McIlroy.
Clarke moved up from 111th to 30th with his triumph at Sandwich two weeks ago.
McDowell is ranked 12th while Harrington has slipped to 64th in the latest standings.
McIlroy and McDowell represented Ireland - in golf the Republic and Northern Ireland come together - on the last occasion the World Cup was staged two years ago.
On that occasion, the Irish duo finished second to Italian brothers Edoardo and Francesco Molinari at the Mission Hills venue in China.