Sharapova was defeated by Timea Bacsinszky in a tight game, losing 7-6 (3) 7-5, a result which broke the hearts of the local crowd who were supporting the Russian world number four.
"There were a lot of, you know, times in the match where I did everything right for the first few balls and then didn't execute in the points," Sharapova said.
"I think I always allowed her to get another ball back and to make me play another ball. Then obviously that didn't help me, because I was making more mistakes."
Switzerland's Bacsinszky will go on to play either Casey Dellacqua of Australia or Denmark's world number eight Caroline Wozniacki in the quarter-finals.
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Czech third seed Kvitova defeated compatriot Karolina Pliskova 6-3, 2-6, 6-4 to seal her place in the last eight.
Kerber, the seventh seed in Wuhan, lost only two games in her match with Barbora Zahlavova Strycova of the Czech Republic, crushing her opponent 6-1, 6-1.
"I played a very good match. It was tough, because Barbora is a great player and she played very well," Kerber said.