World No. 1 Serena Williams defeated Ana Ivanovic in two straight sets 6-4 6-4 in the opening day of the WTA Finals in Singapore on Monday.

The defending champion started off smoking as she took advantage of the 26-year-old Serb who seemed to be nervous at the beginning of the first set as Williams jumped out to a 4-1 lead.

Like Us on Facebook

The Toray Pan Pacific champion Ivanovic collected herself and bounced back three straight games to tie the set at four apiece and even had a golden opportunity to break Williams again but failed after she hit a routine volley long and went out of bounds.

Williams went on to win the set after breaking Ivanovic for a third time.

In the second set, both players exchanged breaks early but the 18-time Grand Slam champion was more composed as she broke Ivanovic late in the set to finish the match in an hour and 18 minutes.

The four-time tournament champion converted a total of 12 service aces in the match compared to none for Ivanovic and committed less unforced errors while the Serb had seven double faults which proved costly in the match.

"I'm really excited with how I played the match," Williams said. "I've been working hard and am glad to be here. Today I was really fighting all the way."

Williams was playing in her first match after Beijing where she pulled out of the tournament due to a left knee injury.

"It felt okay on the court today," Williams said. "I felt the knee a little bit. But compared to what it felt like in Beijing, it feels so much better."

Ivanovic, who pulled out of the Generali Ladies Linz early this month because of a hip injury, can't hide the fact that she was disappointed with herself after the match.

"I'm definitely very disappointed that both sets I made few easy errors in the last service game," Ivanovic said. "Especially in the first set, you know. I had a break point in 4-all, which I didn't take and kind of got down a little bit on myself."

Tagsserena williams, Ana Ivanovic