The remarkable comeback of Kim Clijsters gathered pace at the US Open, underlining her growing threat to the domination of the Williams sisters.
The 26-year-old Belgian defeated 14th seed Marion Bartoli of France 5-7,6-1, 6-2 on Wednesday to reach the third round.
In just her third tournament back after a two year 'retirement' during which she got married and had a baby daughter, 26-year-old Clijsters started slowly but moved up through the gears to stun the former world top tenner.
She will next play another Belgian, Kirsten Flipkens, for a place in the last 16, where she could run into Venus Williams, who is struggling with a knee injury.
The 29-year-old American, who won back-to-back titles here in 2000 and 2001, wore a heavy white strapping to support her left knee in her tie against compatriot Bethanie Mattek-Sands, but she was rarely stretched and won 6-4, 6-4.
Younger sibling Serena, who is in the same half of the draw, later produced an awesome display of power hitting to demolish Hungary's Melina Czink 6-1, 6-1 and reinforce her position as the tournament's outstanding favourite.
Clijsters said that the key to her win over Bartoli had been a tactical change she had made after losing the first set.
"She was playing really well and dominating the points and my forehand was not going the way I wanted it too," she said.