DUBLIN - Rory McIlroy, suddenly struggling with his US Open title defence looming, will try to get back on track this week at the US PGA Tour's Memorial. Two straight missed cuts at prestigious events, the US tour's Players Championship and the European Tour's BMW PGA Championship at Wentworth, have seen McIlroy surrender the world number one ranking. Things got so bad at Wentworth that the 23-year-old's frustration spilled over with a tossed club. "When you've went on a run when you've hardly finished outside the top five, and then all of a sudden two missed cuts, it's more of a shock than anything else," McIlroy said Wednesday as he prepared to tee off on Thursday in the $6.2 million Memorial, hosted by Jack Nicklaus at Muirfield Village. "Just a little bit surprising, and it's something I haven't really had to deal with in a while, and I just have to knuckle down and figure it out and get back to the way I was at the start of the year." With the US Open, the second major championship of the year, due to tee off at the Olympic Club in San Francisco on June 14, the Memorial will give McIlroy a chance to test himself against some of the game's best. World No. 1 Luke Donald of England, Masters champion Bubba Watson, Tiger Woods and Phil Mickelson are here, along with defending champion Steve Stricker. No matter how this week goes, McIlroy has scheduled himself to play the St. Jude Classic next week to give himself more golf before he defends the US Open title he won at Congressional last year. "I just feel like I need more rounds," he said. "These two-day weeks aren't really that good for me."