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Jordan Spieth vowed to learn from his mistakes after struggling to maintain his lead and his composure on a windswept second day of the Masters.
Spieth turned a two-shot overnight advantage into a five-shot lead with early birdies on Friday, but then four-putted the fifth hole and struggled to a 74 - his worst score in 10 rounds at Augusta National - to finish just a shot ahead of Rory McIlroy.
The defending champion was visibly - and audibly - annoyed at being timed for slow play on the 11th, but crucially saved par from sand on the 18th to become the first player in tournament history to hold the outright lead after six consecutive rounds.
" I wouldn't say it was unfair," said Spieth, who became the first player to be given a "monitoring penalty" for slow play under new European Tour rules in Abu Dhabi in January.
"I would say have fun getting put on the clock at 11 of Augusta, and then play 11 and 12 rushing with gusting winds. It's not fun. It's not fun at all.
"We were way behind, so the only thing that I tried to ask to the rules officials that we could have a warning a couple holes in advance when it looks like you're falling somewhat behind. Because I don't know when we started not getting warnings, but we haven't been warned in a while. It's just, 'Hey, you guys are being timed'.
"I'm more than happy to take a bad time, and I had a 70?footer on number 11 across the green that I felt like I really needed to rush. Michael (Greller, his caddie) said, 'If you get a bad time, you get a bad time'.
"But then after that you're still on the clock and you've got gusting winds. You step off of one more shot and the rule says you get a stroke penalty. So it makes a difference."
Spieth, who will be paired with McIlroy in the final group on Saturday, added: " I think I can use the back nine as a learning experience. It was very tough to stay cool. I mean, it's a lot easier said than done. You could say, 'You looked like you got emotional out there'. I mean, you guys try it. That was a hard golf course!
"This has now gone to very much a US Open?style of play, on challenging greens."