Hewitt started strongly before losing 7-5 6-1 to Czech Radek Stepanek, but his second set fade out had nothing on that of Tomic.
Tomic admitted the pressures of the tennis tour were taking their toll, the 19-year-old winning just eight points in a miserable second set as he went down 6-4 6-0 to Germany's Florian Mayer.
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, who stands 6' 5" (196 centimetres) tall, 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," added the Australian, who turns 20 later this month.
Mayer, who will next play US Open champion Andy Murray, said he was surprised at how easily Tomic had folded in the second set.
"Of course, second set we don't have to talk about it, he probably didn't try his best, but I'm happy, easy match, not too long on the court," he said.
"In sports you want everybody to fight," he added.
"But it's tough, I know it from my side. I also don't fight every match because it's tough, but I try my best."
Matosevic lost 7-6 (7-4) 6-3 to Canadian 12th seed Milos Raonic.