Rory McIlroy has expressed frustration at the state of his game after shooting 78 in the first round of the Memorial Tournament at Muirfield Village.

The two-time Major champion started with a birdie at the 10th, but six bogeys and a double saw him finish six-over and put him in danger of missing the weekend.

"It was just a bit of a struggle out there," Sky Sports News quotes the Northern Irishman as saying. "The game just isn't all there at the minute, but I'm working hard and I'm trying to figure things out.

"I'll head to the range and practice most of the afternoon. I need to shoot something like 66 or 65 to probably make the weekend.

"That will be the target tomorrow, try to shoot the lowest score possible and see what happens."

McIlroy missed the cut at the BMW PGA Championship at Wentworth last week.