"I've just never putted on greens like this before, if that's an excuse. It was so fast, I didn't even know what to do out there. It was like putting on ice.
"Probably my dad could have putted better than that, but, it's good experience and hopefully I'll put up a better number tomorrow."
Five dropped shots over the first six holes included three three-putts for the New Zealand number one - a start which put a major dent in his hopes of pulling off a shock win this week..
To his credit though, Lee battled on to post birdies on the eighth, 10th and 12th on his way to a seven-over par 79.
Lee enters tomorrow's final round on five-over par, eight shots adrift of Spieth - who leads by one on three-under after blowing a four-shot advantage with a bogey, double bogey finish. American rookie Smylie Kaufman is second on two-under while the tie for third a further shot back includes Hideki Matsuyama and, incredibly, 58-year old Bernhard Langer, the 1985 and 1993 champion.
Spieth's late stumble has also opened the door to a raft of other players tomorrow, including a dangerous trio on even par of Dustin Johnson, Jason Day and Danny Willett.
Meanwhile, McIlroy's hopes of completing the career grand slam have taken a hit, scoring a five-over par 77 today to be five shots behind.
Despite today's disappointment for Lee, he still has a huge amount to play for in tomorrow's final round - where a top 12 finish would earn him an automatic invitation to next year's Masters.
"That's very important and I'll be very happy to finish high up there. But I want to go out there and just learn how to putt on these kinds of greens," he said.
"I'm not going to put too much pressure on myself, I just want to learn. I gained a lot form that experience today, I've definitely learned I can compete in majors.
"There was a lot of stress out there. I'm mentally pooped right now."
Lee's round:
7:13am: Lee opened round three with a bogey on the first to drop to -1, three shots off the lead.
7:23am: Quickly recovering with a par, Lee heads to the third hole tied for fifth with Japan's Hideki Matsuyama.
7:27am: After reaching the green in regulation, Lee two-putts for a par on the third hole.
7:38am: Lee bogeys the fourth. +2 for the round and even for the tournament.
7:55am: Lee with back-to-back bogeys, now sits at +3 for the day and +1 for the tournament. Stands alone at 12th place. Jordan Spieth is holding on to the lead, -1 through four holes. -5 for the tournament.
8:23am: After recording a double bogey on the sixth, Lee recovers with a par on the seventh. Slips into a tie for 18th place, +3 for the tournament.
8:52am: Lee closes out the front nine with par-birdie-par, going out in 40 shots. Currently sits at a tie for 14th. +4 on the day, +2 for the tournament.
9:30am: Lee starts the back nine with a birdie, before erasing that with a bogey on the 11th. Heads to par three 12th hole still tied for 14th.
10:00am: Once again Lee follows a birdie with a bogey, stays at +2 for the tournament. Meanwhile Jordan Spieth extends his lead to -4, with Hideki Matsuyama in pursuit at -3.
10:34am: With three holes to play, Lee has slipped further to +3 after a bogey on 14th hole and a par on the 15th. Moves into a tie for 13th place.
10:57am: Heading to the 18th hole, Lee is now tied for 16th place. After recording birdies on the par three 16th in the first two rounds, Lee had a three-putt for bogey this time around. He parred 17. Now +6 on the day and +4 for the tournament.
