Northern Ireland's Rory McIlroy says he is "concerned" by his form heading into the US Open next week after struggling with driver issues at the Canadian Open. The 36-year-old missed the cut at the Canadian Open on Friday, finishing nine over par and 149th in a 153-man field. The Masters champion shot an eight-over-par 78 during his second round as he struggled to get to grips with a new driver. McIlroy's previous driver was ruled non-conforming on the eve of last month's US PGA Championship, with the Northern Irishman going on to finish 47th in North Carolina. "Obviously going to Oakmont next week, what you need to do more than anything else there is hit fairways.