Li Na, Radwanska safely through in Madrid
Australian Open champion Li Na avoided a repeat of her shock first round exit at the Madrid Open last year with a 6-1, 7-6 (9/7) win over Belgian Kirsten Flipkens on Monday.
The world number two raced through the opening set, but was forced to save two set points in the second before closing out the match in a tie-break.
"I knew it would never be an easy match and even when I won the first set, she was really fighting a lot in the second," said the Chinese star.
Next up for Li is a meeting with compatriot Jie Zheng in round two.
"We are from the same country, we know each other well so I`m sure it will be tough," she added.
Number three seed Agnieszka Radwanska also sealed her place in the last 32 with a 7-6 (7/3), 6-2 win over Australian Open semi-finalist Eugenie Bouchard.
The Canadian put up a strong fight in a tightly contested opening set, but Radwanska`s variety of shot-making allowed her to comfortably take the tie-break.
And the Pole took complete control in the second with an early double break and served the match out to set up a second round clash with Russia`s Svetlana Kuznetsova or French player Alize Cornet.
On the men`s side Japan`s Kei Nishikori kept his recent fine form going after winning the Barcelona Open last week with a 6-4, 6-4 win over Croatian Ivan Dodig.
Nishikori will face Spaniard Guillermo Garcia-Lopez in the second round.
Australian Open finalist Dominika Cibulkova of Slovakia became the first seed to fall on Monday, as she was comprehensively beaten 6-3, 6-0 by 2011 US Open champion Sam Stosur of Australia.