US Open 2015: Rory McIlroy continues to struggle with his putting at Chambers Bay

World No 1 hits round of 70 after more issues on the greens

Rory McIlroy, of Northern Ireland, watches his tee shot on the seventh hole during the third round of the U.S. Open (AP)

How to turn a round of 65 into a 70? Putt like Rory McIlroy at Chambers Bay. McIlroy volunteered the insult himself after failing to advance his cause at the US Open.

The world No 1 was imperious again from tee to green in the third round, his raking drives and laser irons creating chance after chance, particularly on the back nine, where he failed seven times to convert birdie chances from eight feet and in.

And then at the last there was an ironic celebration when he finally got one to drop to save par after that rare thing, being out of position with an awkward lie in a bunker. “Yeah, it took a while to hole one there. It was just nice to see one drop,” said McIlroy after closing on four over par.

“Whenever you start to miss a couple you start to get a little tentative. You start to doubt yourself. You start to doubt the greens a little bit. And then it just sort of snowballs from there. I holed a few nice ones early on, but once I missed a couple it got into my head and couldn't really get out of it.”

Pity because McIlroy is a thing of golfing beauty when the flat stick responds. A birdie at the second and seventh, a ridiculously difficult uphill dogleg measuring upwards of 500 yards, had the pulse racing. And then he missed a tiddler at the tenth and another at the 12th that would have seen him back to level par and only five behind the overnight lead.

The back nine was excruciating to watch, exquisite ball striking combined with timid putting. “I had a chance today to go out and try and shoot a good score and get myself somewhat back into it. And for half of the round today it looked like I would. And it was just another disappointing finish.”

Joint leader Jordan Spieth was just setting out as McIlroy was deconstructing his round. Two monsters from 25 and 35-feet knocked in with ease at the second and third respectively took him to seven under par and into the lead alone.

There could not have been a more telling demonstration of the difference between the top two players in the world this week, prompting McIlroy’s Ryder Cup captain at Gleneagles to post the question: “How good a player would Rory be if he could putt like Jordan Spieth?”