Aggression powered Maria Sharapova to victory over Italy's Sara Errani in her opening match at the $4.9 million WTA championships here, the Russian said.
In a repeat of their only previous meeting in June's French Open final, Sharapova emerged victorious by a score of 6-3, 6-2 against Errani Tuesday.
Cautious play allowed Errani to control the start of the match, when the first four games all went with serve, Sharapova said.
"It was a slow start. I gave Sara a lot of time, and that's what she likes," the world No.2 said on the WTA website.
"I think the points were going a bit too long. I just tried to step in and be more aggressive after that, and it really helped me."
World No.7 Errani said she had "played a good match" but that Sharapova had been too strong for her.
Sharapova plays fourth-ranked Agnieszka Radwanska of Poland in her next match, part of the round robin stage that sees the eight players split into two groups of four.
The other player in Sharapova's White Group is Petra Kvitova of the Czech Republic, who was beaten 2-6, 2-6 by Radwanska.