For a shot at the semi-finals, top-seeded Sharapova will meet another hard-hitting Russian, 19-year-old Anna Chakvetadze.
They have met three times before but Sharapova had trouble recalling that when interviewed after last night's match.
"I've never played her before
. Yes, I have. What am I saying?" Sharapova said.
"She's had some great results in the last couple of months. Another great Russian coming up so I'm looking forward to that."
Chakvetadze, the 12th seed who won at Hobart in a warm-up to this event, has a walkover against Sharapova in last October's Kremlin Cup in Moscow as her only victory.
The last time the pair actually played was in Los Angeles in 2005, when Sharapova won in three sets.
Chakvetadze said she was an improved player.
"Yes, I think so because now I have more confidence and I know how should I play," she said.
"I mean, if I use my game plan, you know, correctly, then I can win I think."