Rory McIlroy of Northern Ireland tees off at the fifth hole during day two of the WGC-HSBC Champions tournament at the Shanghai Sheshan International Golf Club on Friday. Photo: AFP

 Rory McIlroy played 10 immaculate­ holes at the World Golf Championship HSBC Champions on Friday before the wheels, while not exactly coming­ off, had a serious wobble in Shanghai.­

As he stood on the 11th tee, he had hit 10 greens in regulation, made three birdies and never looked like dropping a shot. He had extended his two-shot overnight lead to three and was 10 under par.

The tough 456-yard par four lay ahead, having been the scene of his only bogey during his sumptuous opening day 65.

But McIlroy found the same deadly fairway bunker on the right as on Thursday, and he agreed that knocked him sideways a little.

"It played on my mind a little bit," McIlroy told AFP straight after his round. "To make the same mistake twice into that bunker was very frustrating.

"I didn't have any bogeys up to that point and I wanted to play bogey-free. Obviously that didn't happen."

He fell back to nine under­ where he was joined briefly by Dustin Johnson of the United States, who went on to shoot a course record-equaling 63 and move to 12 under for the tournament­ - five clear of McIlroy, who dropped two more on the way in, and fellow Americans Boo Weekley­ and Bubba Watson.

"The driver's good when it's going well but when I hit a couple of bad ones it knocks my confidence a bit so I just need to go on the range and hit a few drives and get the confidence back," McIlroy said.

"I'm still working a bit on my swing so that is what it was really. You can let shots slip away pretty easily­, there's a couple of tough holes on the back nine."

McIlroy, who led by two shots at the start of the day, was clearly exasperated with his stuttering finish for a level-par round of 72, including a bogey six at the 18th, on a low-scoring­ day when 37 players shot sub-par rounds.

"I did well on the front and then I just let it get away from me a little bit," he said.

"I didn't really have many chances on the back nine. I had a chance at 10 and a chance at 12, apart from that I was just trying to scramble for pars."

A particular source of ire was his inability to capitalize on the par fives.

"The important thing around this golf course is you have to play the par fives well," the 24-year-old world No.6 from Holywood, Northern Ireland, said.

"I played the par fives well yesterday­, shooting a good score. Played them in even par today and shot an even-par round. It's a big difference."­

It is just the halfway point, and McIlroy took the positives from playing 27 almost­ flawless holes on Thursday­ and Friday, saying the back nine hiccup­ "was just one of those things."

"Hopefully I've got it out of the way now and I can shoot a couple of scores in the 60s at the weekend and give myself a good chance of the win."

China's Liang Wenchong ranked 11th on five under.

AFP - Global Times