However, she has been in decent form in China and was a 7-5 6-3 victor against Magda Linette in the second round in Tianjin.
Venus Williams was knocked out in the second round of the Hong Kong Open by 19-year-old Naomi Osaka.
She saw off 71st-ranked Linette in just over 98 minutes to reach only her second quarter-final since her return to action.
Linette was dispatched by Sharapova in straight sets 5-7, 3-6.
The Russian's first-serve percentage was only 59 per cent, but she was able to overpower the Pole and saved nine break points to get the job done in two sets, setting up a meeting with Stefanie Voegele - who ousted Yulia Putintseva in the final match of the day.
Petra Kvitova, also seeded second, suffered a shock defeat in her first-round match at the Tianjin Open.
Sharapova, a five-time major-winner, is now ranked a lowly 86 in the world, and she needed a wildcard to enter the Tianjin tournament.
She also clinched the silver in the 2012 Summer Olympics in London and was the 2008 Federations Cup champion.
Sharapova, who was beaten by Simona Halep in the third round of the China Open last week, took a 4-3 lead in the first set before Linette hit back.
After a 15-month long suspension for violating anti-doping regulations, Sharapova made her comeback to tennis in April at Stuttgart, where she stormed into the semifinals round of the tournament.