World number one Rory McIlroy said he was disappointed with the finish to his third round at the Masters.
McIlroy (68) was making a charge up the Augusta leaderboard when he was six under through 15 holes, but a bogey-par-bogey finish left him 10 shots shy of leader Jordan Spieth in a tie for fifth.
The Northern Irishman all but conceded Spieth was out of reach with 18 holes to play, but was more disappointed he could not cap a blistering round off - after making an eagle and four birdies, and going bogey free until the 16th.
"I got off to a good start. Sort of the way I wanted to play the front nine. I had not really played the front nine too well the last couple days, so to play them under par is nice," said McIlroy, who finished the day at six-under overall.
"Made a couple good birdies on 13 and 15.
"Felt like the other holes on the back nine were playing pretty tough with the pin positions and a bit of a swirling wind.
"Got it to 8 under par [overall] through 15, and then a disappointing finish.
"But overall felt like I played pretty well; and as I say, just a little disappointed the way I finished."
McIlroy said he would have to post a score in the low 60s on Sunday if he was to win his first green jacket and complete the career grand slam.
"Everyone knows we all know pretty much where the pin positions are going to be tomorrow," he said.
"And there's some holes that you can get close to and be aggressive and there's some holes that you can't.
"So again, try and get off to a good start like I did today, and if I can do that, you know, it really depends on what the guys do the back nine.
"But if I was to go out and shoot 30, yeah, it's going to look, I'm going to need something basically around 61, 62 to have a real chance. I'm not sure that's going to happen but we'll see."
Spieth has shot up the rankings during his hot 2015 season, but McIlroy said he was unconcerned the 21-year-old American would derail him from top spot anytime soon.
"No, not really," replied McIlroy, when asked about the threat of Spieth to the top ranking.
"I just have to worry about myself and try and play the best that I can. I know if I do that, then that number one position is pretty safe.
"He's obviously been playing great golf since the end of last year, a couple of wins and winning again and being in contention, basically, every time he plays.
"He's playing very well, but I know I have the capability to do the same thing."