Rory McIlroy is about to discover just how much he has learnt from what happened at The Masters two months ago.

Unable to hold onto a four-shot lead on the final day at Augusta - he recorded a nightmare 80 and finished 10 behind - the 22-year-old Ulsterman resumes the US Open on Saturday a massive six in front of YE Yang after another fine round at Congressional.

Nobody has ever led the event by more at the halfway stage and nobody has ever matched McIlroy's 11 under par total of 131 for the first two rounds.

But although Tiger Woods, the only other player to be six ahead after 36 holes, went on to win the 2000 championship by a major record 15, people are still intrigued to see how golf's most exciting young talent handles things from now on.

And if McIlroy appears to have a swagger on his return to the course, rest assured it is not because he believes his first major is in the bag yet.

"After Augusta I said I needed to be a little more cocky, a little more arrogant on the golf course and think a little bit more about myself," he said.

"I just try and have a bit of an attitude. When I get myself in these positions I have to really make sure that I don't get ahead of myself and don't start playing defensively.

"Even if you get four, five or six ahead of the field you're trying to get seven, eight, 10, whatever ahead."

Amazingly, 10 was indeed what his advantage was when he birdied the 17th hole of his second hole - Yang had yet to tee off - and at that moment he was the first player to reach 13 under in a US Open.

A bad drive and then a second into the lake on the ferociously difficult 18th, however, led to a double-bogey six.

It did not appear to have knocked him back too much, though, on a day when he also sank a 113-yard pitch for an eagle two at the eighth.

"It's been two very, very good days of golf. I've put myself in a great position going into the weekend, but I know more than probably anyone else what can happen, so I've got to stay really focused and try and finish this thing off."

Korean Yang, the only man within nine shots of McIlroy overnight, has far from conceded defeat yet.

He is best known for coming from two behind Woods on the last day of the 2009 US PGA to win by three - the first time in 15 majors that the then world number one had lost a 54-hole lead.

But there is also last year's Korean Open to give Asia's only major champion encouragement. He won that from 10 back after 54 holes.

"Anything can happen in golf really," said Yang after responding to McIlroy's 66 with a 69 on Friday.

"I know it's sort of a different kind of level of golf tournament, but still there are many amazing things that happen in golf.

"I do have a strategy and that's just to zone out everything around me and just play my game. Just imagine I'm having a practice round."