Australian teenager Bernard Tomic admitted on Tuesday that he had given only "85 percent" in his 6-4, 6-0 defeat at the Shanghai Masters, saying the pressures of the tennis tour were taking their toll.
The 19-year-old won just eight points in a miserable second set of his first-round clash against Germany's Florian Mayer for yet another early tournament exit in a disappointing season.
His Shanghai flop comes just weeks after he was branded "disgraceful" by Davis Cup team captain Pat Rafter following his US Open defeat at the hands of Andy Roddick
US tennis great John McEnroe said Tomic seemed to give up during his 6-3, 6-4, 6-0 loss to Roddick in the second round at Flushing Meadows.
And on Tuesday the Australian admitted he was having problems with the mental side of his game as he adjusted to life on the gruelling tennis tour.
Tomic admitted he only gave "about 85 percent", adding: "Today I gave 100 percent in the first set. I felt in the second set, my 100 percent wasn't even close to where it should be... the mental skill is one of my biggest problems."
Tomic, who has slipped to 43rd in the rankings after hitting a career-high of 27, admitted it had been tough going in 2012 after a breakthrough year in 2011 during which he reached the Wimbledon quarter-finals.
"It's been a long year," he said. "I played a lot of tournaments. Haven't had time to rest. I think I only rested one week after Roland Garros.
"I think it was the wrong sort of move that I made. I think it's costing me now the last few months. My performance has not been as good.
"It's been a massive road this year. I didn't plan my schedule as I should have and it's cost me a lot of matches that I probably should have won," he added.