Sharapova, the runner-up in Melbourne a year ago, lost the first game of Sunday's match but then won 12 consecutive games in gaining a spot in the quarterfinals. She opened her tournament with back-to-back 6-0, 6-0 wins and beat Venus Williams 6-1, 6-3 in the third round.
Sharapova has dropped her serve just once in the tournament and saved all three of the break points she saw against Flipkens. She piled up six breaks of her own in winning 61 percent of the points off Flipkens' serve.
Makarova had three breaks in taking the first set and cashed in her only break opportunity for the only break in the second.
Radwanska had just four unforced errors and saved seven break points in a 6-2, 6-4 win over 13th-seeded Ana Ivanovic. She won 71 percent of the points on serve, firing seven aces without a double fault. Radwanska is 13-0 this year without dropping a set.
Li defeated 18th-seeded Julia Goerges 7-6 (8-6), 6-1 finishing off all five of her break chances. That includes going 3-for-3 in the second set when she won more than two-thirds of the points.
Sharapova draws Makarova in the quarterfinals. She is 4-0 in her career versus Makarova, including a straight-set win in the Australian Open quarterfinals a year ago. Li is 5-4 lifetime versus Radwanska. She's won their last three meetings.