Rory McIlroy gave himself a timely boost for this month's US Open by ending a week of superb putting and accurate driving with a four-under 68 in the final round of the Memorial tournament.

McIlroy completed his 18 holes and set the clubhouse mark of 13-under before a lengthy delay at Muirfield Village due to the threat of lightning.

The world No.3, who birdied three of his last four holes, then watched as he crept up the leaderboard to eventually finish in a tie for fourth behind winner William McGirt.

McIlroy said the only area of his game that still needed some work ahead of the US Open at Oakmont from 16-19 June was his mid-iron play.

"I expect a little bit of a tougher test at Oakmont, I think, but I feel like my game's in good shape," the 27-year-old said.

"Off the tee I was really good this week, and I feel like my putting improved quite a lot.

"So all things considered, it's been a decent week. Time to get ready for Oakmont in a couple weeks' time."
              
Asked what he needed to work on as he prepared for the year's second major, McIlroy replied: "My iron play hasn't been great. I'm just not hitting the ball close enough to the flag with my mid-irons.
              
"I need to work on that a little bit, try to shallow out the plane a little bit. I've been getting a little steep with my short irons. That's what I'll be working on primarily from now until Thursday week."

The four-times major champion created a bit of a stir when he changed his putting grip for the Memorial tournament from the left-hand low method he employed when he won the European Tour's Irish Open two weeks ago.

However, McIlroy said it had not been a difficult decision to make the switch before adding: "I've never relied on my putting to play my best golf.

"Obviously, when you're winning tournaments, you need to hole a few putts, but ... I'd be way more comfortable changing my putting grip week to week than I would be trying to tinker with my swing or do something with my long game."

McGirt took a share of the overnight lead into the final day and a bogey-free round of 71 saw him enter a play-off with Jon Curran as the challenges of Matt Kuchar and Dustin Johnson fell short.

With both Americans looking for their first PGA Tour triumph there was plenty of tension, and adrenalin got the better of both players on the second play-off hole as they overshot the 18th green.

After Curran failed to get up and down, McGirt holed a six-footer for the victory.