Having stunned the golfing world the previous day when he made a second consecutive cut on the PGA Tour, the 14-year-old struggled off the tee before finishing at two-over 218, stone last in the 71-strong field.
"I just didn't do very good in the morning and was definitely in trouble with my driver," Guan, who is playing on a sponsor's exemption this week, told Golf Channel after mixing three birdies with five bogeys and an ugly triple at the sixth.
"I played pretty good in the middle of the round and made a couple birdies but still, it was not a very good round for me."
Guan covered the back nine in two-over 38, signing off with a bogey at the par-five last after playing a poor third shot out of a waste bunker at the TPC Louisiana, where alligators lurk in many of the water hazards.
"He hits the shot and he says with a smile, 'Hey, there's a little alligator right here'," Guan's caddie, Todd McPherson, told reporters. "People forget that he's still a kid.
"Yes, he pays attention to all the little things that go with playing good golf ... when it's time to hit a golf shot, he hits the shot. But at the end of the day he's still a kid."
Guan, who became the youngest player to make the cut in a major championship at the Masters two week ago, said he had not committed to play in any future PGA Tour events.
"I am not sure right now," the eighth-grade schoolboy said. "I intend to play the U.S. Open qualifier (next month in Dallas) and probably after that I will go back to China."
Asked whether he had been approached to compete in other PGA Tour events via a sponsor's exemption, he replied: "No, not yet."
Guan, who booked his place at the Masters by winning last year's Asia-Pacific Amateur champion, had thrilled the large galleries watching his every move this week as he opened with scores of 72 and 69.
"I feel okay with them watching me," he smiled. "The people here are really good, and my parents are following me too. I'm having fun."
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