Rory McIlroy was utterly frustrated with the greens but hopeful that he could regain some confidence in his putting in time to rescue his US Open challenge at Chambers Bay.

The world No 1 missed short putts and bogeyed two of his last three holes to cap a tough day with the blade as he had 30 putts in a two over 72 that left him seven strokes adrift of early leaders Henrik Stenson and Dustin Johnson.

Playing in cool, windless early conditions when the course was playing at its softest and easiest, McIlroy birdied the 11th after a super approach crept back to just six feet and he rolled in the putt. 

But the Holywood man, one of the streakiest putters at the best of times, holed little after that to put himself under pressure for Friday’s second round in what are sure to be tougher conditions on greens that deteriorate as the day goes on because of the meadowgrass that has invaded them.

He bogeyed the 14th, missed three-foot par putt after bunkering his tee shot at the par-three 15th but birdied the 16th to turn in level par 35.

But he could’t make a birdie on the way home and bogged the seventh, pulling a four footer well wide, before burning the edge for birdie at the par-five eighth and then bogeying the par-three ninth after bunkering his tee shot and splashing out to around four and a half feet.

“It was frustrating, especially how I felt I hit the ball from tee to green,” McIlroy said. “I drove the ball great. I hit my iron shots very, very well. Even when you hit good iron shot, getting it to 25, 30 feet is a good shot at times. I felt like I gave myself enough chances out there to convert a few and wasn't able to do that. 

“Missed a couple of short-ish putts on the last few holes there and definitely thought it was a day where you could shoot under par and I didn't take advantage of that.”
 
Asked about the greens, he said: “They are not the best that I've ever putted on. I still feel like if you make a good enough stroke and you have the right speed, there's a good enough chance the ball will go in.

"I need to find a rhythm in my stroke over the next three days, work a bit on the putting green and hopefully it will be better tomorrow.” 

He still believes there’s a low score to be had if he can “keep hitting the ball as well as I did off the tee.”
 
“I just didn't quite have it with the putter today and that's something that I need to get right over the next three days if I want to have a chance.’

Asked if his missed putts came from misreads, poor strokes  or poor greens, McIlroy said: “A little bit of both. I think there were a couple of misreads and there were a couple of bad strokes as well. It is just hard whenever the ball is not rolling the way you would want it to on the greens. 

“It is hard to pick a line and just trust it. That;s what I’ve felt. Then you start to make tentative strokes and then you are not getting a true roll on the ball and there is no chance of the ball going in. 

“I just need to work on that and I will do a little bit of work on the putting green before tomorrow’s round and see if I an figure something out before going out there tomorrow. 

“The course was set up fair that you could do a score as Henrik and Dustin showed. It was definitely out there with not much breeze at all. 

“If you could hit the ball well and convert a few of your chances there was a score in the mid 60s out there.”

McIlroy still believes that Chambers Bay is a US Open course that you can attack. 

“If anything today just reiterated what I felt coming into this week, which is that you can be very, very aggressive,” he said. “You can be really aggressive with your tee shots and go at certain pins. It is not a typical US Open where you have to play a game of chess. You can stand up and be really aggressive.”

Outside the cut mark for the Top 60, he knows can’t afford another poor day and feels confident he’s close to playing well. 

“I think more of the same from tee to green. If I can do that I will be very happy. I will just try to figure something out on the greens and try to get some sort of rhythm going in my stroke for the next three days.” 

If McIlroy was upset with his putting, McDowell was left to rue an even more disappointing day as he had 35 putts in a four over 74.

A double bogey six at his opening left him on the back foot and while he did well to birdie the 14th (he holed a 35 footer) and 16th to get back to level, he played his last 11 holes in four over par with bogeys at the 17th, second, sixth and ninth.