Jordan Spieth carded the lowest halfway total in Masters Tournament history to take a massive step closer to a first Major Championship at Augusta National.
Spieth added a second round of 66 to his opening 64 to post a total of 130, one shot better than the previous best set by Ray Floyd in 1976.
That also equalled the 36-hole record in any Major shared by Sir Nick Faldo, Brandt Snedeker and Martin Kaymer, and at 14 under is the lowest 36-hole score in relation to par.
Faldo was 12 under on his way to winning the 1992 Open Championship at Muirfield, with Snedeker and Kaymer ten under at the 2012 Open and 2014 US Open respectively.
Spieth was runner-up here last year and came into the week having finished first, second, and second in his last three events.
"I have been on my game and coming to a place that I love," Spieth said. "It's special to be here and just be in the tournament let alone out front.
"I just need to keep my head down, set a goal for myself. It's definitely going to be more challenging and I am going to have to be aware of that and be okay with a bogey or two."
At 14 under par Spieth was four ahead of fellow American Charley Hoffman, who had two holes to play.
Tiger Woods was three under for his round and two under overall in just his third start of the year, while World Number One McIlroy was bidding to become the sixth player to complete the career Grand Slam, but found himself 12 off the pace as he set off and started his second round with a bogey on the first and birdie on the second.
Ernie Els was refusing to give up hope of catching Spieth despite being nine adrift after adding a 72 to his opening 67.
"Jordan is playing unbelievably well and obviously we're all watching the leaderboard," Els said. "But we know how far there is to go. Front runners tend to do well here, but there have been some really good comebacks, so it's a big weekend ahead.
"He's not thinking about anything right now and that's a great place to be at.
"I'd really like to shoot two 67s and see where that leaves me. That'd make me 15 under and that's about as good as a man can do.
"If it keeps blowing like this and the nerves get going... I don't want to wish badly on anyone but if he takes his foot off the gas or has a bad break here and there, it really gives you thought of catching him."
Hoffman bogeyed the 18th to card a 68 and finish nine under par, leaving Spieth five shots clear and currently equalling the record for the largest halfway lead in the Masters.
That is shared by Herman Keiser (1946), Jack Nicklaus (1975) and Floyd - with all three men going on to win.
McIlroy was starting to become more concerned with making the cut than winning after bogeys on the fifth and seventh dropped him to one over par and just two shots inside the projected cut.
