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.

With a new 44-inch driver in hand, McIlroy found just 13 of 28 fairways in Toronto and he made a quadruple-bogey eight on the par-four fifth hole after a disastrous tee-off.

“Of course it concerns me,” said McIlroy.

“You don’t want to shoot high scores like the one I did today. I felt like I came here, obviously with a new driver, thinking that sort of was going to be good and solve some of the problems off the tee, but it didn’t.

“Obviously going to Oakmont next week, what you need to do more than anything else there is hit fairways. I’m still sort of searching for the missing piece off the tee. Obviously for me, when I get that part of the game clicking, then everything falls into place for me. Right now that isn’t. Yeah, that’s a concern going into next week.”