CARNOUSTIE, Scotland, July 19 (Reuters) - They say the key to a good score around Carnoustie is to make your birdies on the first 14 holes then hang on.
Defending champion Jordan Spieth managed the first part on Thursday but failed miserably with the second, leaking four shots in his final four holes to slide back into the pack with a disappointing one-over 72.
Two birdies in his opening four holes offered early promise for the American but even with fickle Scottish weather in relatively benevolent mood he discovered the sprawling old course still packs a punch.
The 24-year-old double-bogeyed the par-four 15th after suffering what he described as a "brain fart," bogeyed the brutal par-three 16th and then leaked another shot on the last after driving his tee shot into Barry Burn.
"Felt like a missed opportunity," three-time major champion Spieth, who has had an up and down year by his standards, told reporters.
"I felt like I was really going well. I was putting the ball where I needed to. It was a clean round of golf, just the decision-making that's cost me.
"But the misses towards the end were the exact misses that I've been having and I'm working away from. My swing just didn't quite hold up to the end of my round."
It all began to go wrong on the 15th where he played conservatively off the tee and then hit his second shot into the face of a deep bunker, giving him an impossible shot.
He could only play out sideways and ended up with a six.
"I just had a brain fart, and I missed it into the location where there was the only pot bunker where I could actually get in trouble, and it plugged deep into it," he said.
"It was a really, really poor decision on the second shot, and that cost me."
Spieth and playing partner Justin Rose found themselves six strokes behind fellow American Kevin Kisner who was leading into the early evening, but the champion still felt it was a recoverable position.
"I imagine this is as easy as the course could play. So I don't see the winning score being any better than it was in 2007 (seven-under) with tomorrow's forecasted tough conditions and Sunday's forecasted heavy winds," he said.
"I think wherever it is Saturday night, it comes back on Sunday too. So it's not a bad place to be. A solid round tomorrow to stay in the top 20, 25 will be the goal, to feel I can do something at the weekend."
Asked what score could win the title on Sunday, Spieth said it was impossible to predict.
"Five-under could win it, five-over could win it. 15-under could win it," he said. (Reporting by Martyn Herman Editing by Ian Chadband)