Top-ranked Serena Williams beat Yulia Putintseva of Kazakhstan 7-6 (5), 6-1 to advance to the second round of the Madrid Open on Sunday.
Williams says ''I felt a little sluggish out there.'' She next faces Lourdes Dominguez-Lino of Spain.
Putintseva broke Williams' serve early to open up a 3-1 lead in the first set. But the defending champion settled down after breaking serve and, once through the tiebreaker, dominated the second set.
Also in the first round, former top-ranked Caroline Wozniacki was ousted by 35th-ranked Yaroslava Shvedova of Kazakhstan 6-3, 6-4.
Serena's sister Venus Williams withdrew early Sunday morning before her first-round match due to back problems.