Reigning Madrid Open champion Iga Swiatek suffered a crushing semi-final defeat by Coco Gauff on Thursday, with the American triumphing 6-1, 6-1.
Iga Swiatek admits the strict doping protocols can be stressful for players but feels like she has "been through the worst" after surviving her positive test over contaminated melatonin.
Swiatek said she made far too many mistakes against Keys on Rod Laver Arena and hoped to draw lessons from it.
The Polish second seed was phenomenal on a gusty day at Rod Laver Arena, powering past the eighth seeded-American 6-1, 6-2 in 1hrs 29mins.
Romania's Simona Halep on Friday rounded on the International Tennis Integrity Agency (ITIA) for discrepencies in the treatment of world number two Iga Swiatek after testing positive for a banned substance.
"The player was provisionally suspended from Sept. 22 until Oct. 4, missing three tournaments, which counts towards the sanction, leaving eight days remaining," the ITIA said in a statement.
The 26-year-old jumped above Poland's French Open champion Iga Swiatek thanks to year-end adjustments in the standings.
Top seed Swiatek, who won the title two years ago, showcased her all-court game in a straightforward 6-4, 6-1 win over Russian Liudmila Samsonova to open the evening session at Arthur Ashe Stadium and warned she was only going to improve.
Four-time French Open champion Swiatek was equally dominant as Sinner as the top-seeded Pole eased into the fourth round with a 6-4, 6-2 victory over Russia's Anastasia Pavlyuchenkova.
French Open favourite Iga Swiatek breezed into the second round at Roland Garros on Monday, beating Ukrainian qualifier Lesia Tsurenko 6-2, 6-0 to extend her winning run to 29 matches.
