McIlroy could only add a 72 to his opening 74 at Carton House to finish two-over-par, with McDowell and Harrington missing out by one shot on one-over and Clarke six-over.
That left former winner Shane Lowry to carry the burden of home hopes as the 2009 champion returned a second-round 70 to share third place on seven under, two shots behind leaders Robert Rock – whom he beat in a play-off four years ago – and American Peter Uihlein.
McIlroy admitted on Thursday he felt “a little bit lost” as he struggles to rediscover the form which brought him five victories last year and made him world No 1.
But the 24-year-old said he would not add either the French or Scottish Open to his schedule ahead of the third major of the year, instead honouring sponsor and family commitments and working on getting the right Nike driver.
“If I did not have those commitments I probably would, but as long as I play rounds and be competitive myself – play with one ball – it’s the same sort of thing,” McIlroy said. “My schedule has been light, but from the Open onwards I am playing seven events in nine or ten weeks.
“It was a new driver in the bag this week, but it’s still not 100 per cent so I will be testing next week, but it’s definitely more swing than it is club. Two weeks is a lot of time to try and get something right and hopefully I will be ready for Muirfield. It’s not great for the tournament that myself, Graeme, Darren, Padraig and Paul McGinley are not here for the weekend, but we have Shane up there and after playing with him for two days I think he has a good chance going into the weekend.”
Scott Henry is the leading Scot – three behind the leaders – after the Clydebank man trimmed ten shots off his opening effort with a brilliant eight-under-par 64 that contained an eagle and six birdies.
A shot further back on five-under is Peter Whiteford, who has rediscovered form at Carton House after describing his performance in last week’s BMW International Open as “pathetic.”
The 32-year-old from Kirkcaldy missed the cut in Munich after hitting rock bottom following a week off to rest his damaged left wrist. But Whiteford was in much better shape yesterday when he carded a second-round 68 to move onto the fringes of contention at five-under-par.
“It was a tough day in the wind but I hit the ball nicely,” he said. “The fact that the majority of the flags were positioned on the right helped me the way I fade the ball so no wonder I had a half decent day.
“Mind you, I was three-quarters the way through my round before I realised that was the case. But even though I had only one bogey, I still left quite a few shots out there, if I’m being honest.
“But, all in all, my game’s coming back. I was terrible in Germany where I came back from a week off like a beginner and hit rock bottom. In fact, I was pathetic. The problem this season has been a lack of consistency. I’ve had three or four decent weeks and about 12 horrendous ones.
“Some of my golf has been good but I need to get rid of the other stuff. I don’t know the reason for my lack of consistency, because I’ve been practising the same way I usually do.
“But there’s no secret to achieving consistency that I know of. Driving used to be one of my strengths and for the past 12 to 18 months it’s been my downfall.
“The older I get the wider I get off the tee, but, having made the cut, I can just enjoy it and crack on from here knowing that I am heading in the right direction again.”
Paul Lawrie is on three-under, one ahead of Stephen Gallacher and two in front of David Drysdale.