The three-time Grand Slam title winner needed only 57 minutes to eliminate Kustova.
"I played a solid game and did everything that I had to do in order to win today,'' Sharapova said. "More importantly right now than ever, is just to do the right things and to work on my game. It doesn't really matter who I'm playing.''
The Russian had surgery for a torn rotator cuff last year and missed the past two Grand Slam tournaments. She said the shoulder hasn't bothered her in Warsaw, and the only sign of the injury on Wednesday were two strips of white tape on her right shoulder.
"I'm really enjoying myself, and after putting in so much work and being out for so long, it just gives you so much satisfaction to know that the work that you put in at some point is going to bring you victories,'' she said. "But right now it's just a thrill to be out there and competing.''
Sharapova, who is playing in her first WTA tour singles tournament in nearly 10 months, is trying to regain the form that led her to the No. 1 ranking in 2005. She slid to No. 126 in the rankings while sidelined with the injury, but despite showing a few signs of rust, she didn't face much of a challenge from the 209th-ranked Kustova.
Sharapova broke the Belarusian in the second game of the first set, and her only slip of the match came when she double faulted when leading 4-0 to hand Kustova a break. But she quickly recovered and claimed the first set with a forehand winner that clipped the baseline.
Despite the two wins in two matches, Sharapova stressed she still faced a long road back to her championship form.
"I think it's going to take time. I think I still need match play, and being in different situations in the matches is going to give me that feeling back and that experience back,'' she said.
Looking ahead to her quarterfinal matchup with eighth-seeded Alona Bondarenko, a 6-3, 6-1 winner over Marta Domachowska of Poland earlier Wednesday, Sharapova said she expects a challenge from the Ukrainian.
"She's in good form, she plays a really good defensive game but she can also step in and hit the ball,'' Sharapova said. "She's a good opponent for me to play.''
In other second round action, sixth-seeded Daniela Hantuchova of Slovakia beat Urszula Radwanska of Poland 6-3, 6-1, Klara Zakopalova of the Czech Republic upended third-seeded Zheng Jie of China 6-0, 6-4, and qualifier Alexandra Dulgheru of Romania upset fifth-seeded Sara Errani of Italy 6-4, 6-3.
Also, Anne Keothavong of Britain downed Jill Craybas of the United States 3-6, 6-3, 6-1, Galina Voskoboeva of Kazakhstan beat Kateryna Bondarenko of Ukraine 6-4, 7-6 (5) and Ioana Raluca Olaru of Romania eliminated Julia Goerges of Germany 6-3, 0-6, 7-6 (3).
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