And the Chinese prodigy was not done, heading out at the end of the day with his idol, Tiger Woods, for nine more holes and taking time for some fun trying to skip balls across the pond at the par-three 16th with Woods and Dustin Johnson.
The 61-year-old Crenshaw, whose career was built on his ability as a putter, mentored the precocious Chinese during their practice round, advising the Asia-Pacific Amateur champion about the notoriously fast, sloping greens of Augusta.
At the 18th, the slightly built Guan hit his approach to the back of the green with the pin on the lower level down front.
Crenshaw stood behind Guan as they looked the putt over and with his longtime caddie Carl Jackson pointed out the line to the hole.
Guan gestured well left of the cup, but tried the line advised by Crenshaw. Hitting the putt ever so gently, the ball barely reached the slope and trickled down, gained speed and rolled about eight feet past the hole.
Then Guan came back and tried it his way.
The willowy thin, baby faced teenager knocked a putt toward the left edge of the big green, running it up into the fringe to slow the ball before it rolled back on the green and curled to within four feet of the cup.
Crenshaw, determined to try the line he had pointed out, made four attempts from the same position and ran all four putts farther past the hole than Guan's initial stab.
"That's great imagination," Crenshaw caddie Jackson told Reuters as they walked from the green. "He's very smart. He's not bashful about this experience and asking questions. He's got talent."
Crenshaw said he thoroughly enjoyed the round.
"He's way more mature than 14," said Crenshaw. "I think we're all asking ourselves what the heck were we doing when we were 14. He's very accomplished and you could just tell that he lives and breathes it.
"He doesn't over exert himself, he's balanced."
Guan was equally impressive in his interview session, as he answered questions in English with a very natural, self-assured demeanour.
Asked if he felt intimidated by joining the 93-player field featuring the world's greatest players, eighth-grader Guan said: "I'm not going to say that.
"I think it's going to be a little pressure to me, but I'm not going to push myself too hard. I'm going to enjoy the game."
Guan will lower by more than two years the Masters' age standard set three years ago by Italy's Matteo Manassero, but the Chinese is accustomed to being a trend setter.
He was the youngest player in the field when he won the Asian-Pacific Amateur that qualified him for the Masters. He was the youngest to win on the China Amateur Futures Tour, the China Amateur Tour and the China Amateur Open, and also won the Junior World Championship.
A relatively short hitter, the smooth swinging Guan outdrove Crenshaw but will be at a disadvantage this week, hitting hybrids or fairway woods into the longer holes.
FINE-TUNING
Guan arrived at Augusta almost three weeks ago to become acclimated and has already played about seven rounds, but will get further fine-tuning from some other giants of the game.
Besides his late-day practice with Woods and another long hitter in Johnson, Guan has arranged a practice round with twice winner Tom Watson and a spin through the Par-3 Contest with three-time champion Nick Faldo.
"I have the confidence and I know I can play well. So I'm going to play like myself," he said. "I'm not going to try to do too much."
Guan took up the game at about age 4, taught by his father and inspired by watching Woods on television.
"When I was probably three or four years old, I was looking at him win the Masters, and it's pretty exciting to watch him," Guan said about four-time winner Woods.
"I played with him twice in the past couple years, and he gives me advice and I will say every time I play with him, I feel a lot better and give myself confidence."
With golf added to the Olympic programme, Chinese officials have begun promoting the sport and Guan said he believed his Masters appearance would help grow the game.
"I think it's good for Chinese golf, and good that more people get to know this game, to pick up this game," said Guan.
