US Open champion Rory McIlroy is in danger of slipping out of contention for the Irish Open title after a miserable front nine in the third round at Killarney on Saturday. McIlroy went into the weekend hoping to overhaul leader Marcel Siem of Germany, who held a six-shot lead over the Northern Ireland star. Siem, at 10 under par, led by one shot overnight from India's Jeev Milkha Singh and Denmark's Soren Hansen, who were tied in second place. But McIlroy's challenge to that trio suffered a serious blow when he double-bogeyed the opening hole in windy conditions. The 377-yard first hole runs alongside Lough Leane, and ater his tee shot finished on the beach in amongst stones, McIlroy advanced his ball only about 20 yards. His third only just made it onto the front of the green and from there he three-putted for a six. That poor start seemed to shake McIlroy's confidence and he dropped another shot on the short third. By the time McIlroy reached the halfway stage, he was still three over for the day and nine shots behind Siem, who starts his round later on Saturday. Northern Ireland's Graeme McDowell, who turned 32nd on Saturday, still has a chance to savour a memorable birthday weekend as he reached the 10th hole at par for the day and four under for the tournament. 2010 US Open winner McDowell started with a birdie putt of nearly 20 feet to reach five under, but he three-putted for a double-bogey five two holes later. Another Northern Irishman Michael Hoey birdied the 384-yard second to move up to seven under for the tournament and into a share of fifth place.