Elina Svitolina's hopes of securing a third successive title in Rome were ended by Victoria Azarenka following Serena Williams' withdrawal.
Former world number one Caroline Wozniacki was unable to complete a first-round match for the second successive week due to a new injury.
Caroline Wozniacki's participation in the Madrid Open was brief, while Elina Svitolina suffered an early exit on day two.
Caroline Wozniacki fell short in the Charleston Open final as Madison Keys won a first clay-court title of her career.
Not since March 2016 had Victoria Azarenka featured in a singles final but the fifth seed will end that drought thanks to Saturday's win.
Angelique Kerber and Garbine Muguruza reached the Monterrey Open quarter-finals.
As Caroline Wozniacki cruised, Madison Keys was forced into a battle at the Charleston Open.
Simona Halep needed two sets and just over an hour to send Venus Williams packing at the Premier Mandatory tournament on Monday.
Petra Kvitova and Caroline Wozniacki continued their runs at the Miami Open.
While most of the stars advanced at the Miami Open, Elina Svitolina and Garbine Muguruza were beaten.