|Second round leaderboard|
|-14 J Spieth (US); -9 C Hoffman (US) -7 J Rose (Eng), P Casey (Eng), D Johnson (US); -6 P Mickelson (US); -5 E Els (SA)|
|Selected others: -2 T Woods (US), R McIlroy (NI)|
Rory McIlroy needs to "shoot a 14-under-par weekend" to have a chance of winning the Masters to complete the Grand Slam at his first attempt.
Northern Ireland's world number one is two under at halfway, 12 shots behind America's Jordan Spieth who shot a six-under 66 and leads the field by five.
"I'll need two phenomenal rounds and Jordan would have to play a couple of average rounds," said McIlroy, 25.
"Neither look like they're going to happen, so it's going to be tough."
|A testing day for McIlroy|
|Rory McIlroy hit 10 of the 18 greens in regulation on day two. Only 21 of the 97 players in the field performed worse.|
McIlroy won last year's Open to add to his victories in the US Open and US PGA Championship to put himself on the brink of becoming only the sixth man to complete the Grand Slam of golf's four majors.
He started the Masters as favourite and made a solid start on Thursday but his one-under-par 71 left him seven behind first-round leader Spieth.
It did not get better at the start of his second round as he completed the front nine in 40, leaving him 17 shots off the lead and beyond the projected cut mark of two over.
However, he improved on his second nine, coming home in 31 with four birdies, an eagle and one bogey for a second consecutive 71.
|Greatest-ever comeback needed?|
|The most notable comeback in Masters history was in 1956, when eventual winner Jack Burke Jr trailed amateur Ken Venturi by eight strokes heading into the final round|
It still leaves McIlroy with an almighty task to challenge for the Green Jacket come Sunday, with 21-year-old Spieth adding a 66 to his first-round 64 to shoot the lowest halfway score in the history of the Masters with 130.
"I'll go out and try and play the best that I can and we'll see where that leaves me," McIlroy added.
"But, with a few more nine holes like the one I just had there, you never know."