World number one Serena Williams overcame a lethargic start to her Madrid Open title defence to seal an ultimately comfortable 7-6, 6-1 victory against teenage qualifier Yulia Putintseva of Kazakhstan in the first round on Sunday.
Chasing her fourth title of the year, Williams was tested by the 88th-ranked Putintseva early in the match on the clay at the Magic Box arena but her superior power told in the end against a woman 13 years her junior.
Williams is making a fourth appearance in Madrid after beating Belarussian Victoria Azarenka in last year's final.
The American 15-times Grand Slam singles champion will meet Lourdes Dominguez Lino in the second round after the Spaniard beat fellow wild card Simona Halep of Romania on Saturday.
"I felt a little sluggish out there, but I'm happy I was able to win the match," Williams told a news conference.
"I obviously have to and want to play better as each match goes on," added the 31-year-old.
Former world number one Caroline Wozniacki, the 10th seed, was upset 6-2, 6-4 by unseeded Kazakh Yaroslava Shvedova in their first-round match on Sunday.
Sixth-seeded German Angelique Kerber had to come from a set down to get past unseeded Su-Wei Hsieh of Taiwan, coming through 3-6, 6-3, 6-2 to set up a second-round meeting with Alize Cornet of France.
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