The Chinese eighth-grader was penalized one stroke for slow play late in the second round Friday, believed to be the first time such a ruling has been made at the Masters.
The penalty could prevent Guan from making the cut, since he needed to be among the top 50 or at least within 10 strokes of the lead.
After Augusta National announced the decision, the youngster was tied for 54th. Tiger Woods, Fred Couples and Marc Leishman were tied for the lead at 5 under — nine strokes ahead of Guan.
Fred Ridley, the club's competition committee chairman, said Guan's threesome was first warned for being too far behind the group ahead of them at the 10th hole. The teenager went on the clock two holes later — an official imposes a 40-second time limit to play a stroke — and gave Guan his first warning at No. 13.
"In keeping with the applicable rules, he was penalized following his second shot on the 17th hole when he again exceeded the 40-second time limit by a considerable margin," Ridley said in a statement.
That turned what would have been a par into a bogey. Guan finished at 3-over 75 for the round, giving him a 4-over 148 total.
"I respect the decision," he said. "This is what they can do."
Augusta National spokesman Steve Ethun said there were no records of the penalty ever being assessed during the Masters.
