Miami - Serena Williams got her quest for a record sixth Miami WTA title off to a brisk start on Thursday with a 6-1, 6-1 victory over Italian Flavia Pennetta.
The world No 1 and top seed, playing her first tournament since falling to Victoria Azarenka in the final at Doha in February, said she didn't feel too rusty, although her footwork could improve.
"I think I missed a few shots, but only because I think I was off footwork-wise," she said. "But it's always just good just to win a match and stay in the tournament and keep going."
Despite the lopsided scoreline, Williams said Pennetta's ability to extend the rallies made the match difficult, although the American fended off all seven break points she faced.
She had 18 break chances against Pennetta, and converted five, saying she felt a little frustrated that she wasn't doing more.
"I felt like I should be putting the balls away for my opponent quick, but she was so quick and she was running every ball down," Williams said.
Her elder sister Venus Williams also advanced, holding on for a 7-6 (7/3), 3-6, 6-4 victory over Japanese veteran Kimiko Date-Krum.
Fourth-seeded defending champion Agnieszka Radwanska, fifth-seeded Li Na of China and seventh-seeded Petra Kvitova of Czech Republic all joined Williams in the third-round.
Radwanska parlayed an early break in each set into to a 6-3, 6-2 victory over Taiwan's Hsieh Su-Wei.
"I was happy to have a quick match," she said. "The first match is always a little bit tough and tricky, especially after Indian Wells, where we had a little bit of different conditions."
Li, playing her first tournament since suffering an ankle injury in her loss to Azarenka in the Australian Open final, downed Kiki Bertens of the Netherlands 6-3, 6-1.
Former Wimbledon champion Kvitova defeated China's Peng Shuai 5-7, 6-2, 6-2.
Serena next faces Japan's Ayumi Morita, a 7-6 (7/2), 2-6, 6-3 winner over Belgian Yanina Wickmayer.
Her five titles in Miami tie her with Steffi Graf, and while she thinks it would be "really cool" to take sole possession of the record, she said she must focus on the matches as they come.
"I have a lot of matches to play," Williams said. "If I can just stay relaxed - I really feel like I can do it, but, you know, I'm sometimes my own worst enemy.
"I just want to get through every match one at a time."
Williams is also vying to maintain her spot atop the rankings. A failure to reach the quarter-finals could open the door for either Azarenka or Maria Sharapova to overtake her.
"It always feels better when you're No 1," Williams said. "There's nothing like when they announce you and they say, The No. 1 player in the world.
"It definitely gives you a little bit more confidence ... a little more pep in your step."
World No 1 Novak Djokovic will lead men's seeds into second-round action in this combined WTA and ATP Masters tournament on Friday, against Czech Lukas Rosol. Third-seeded David Ferrer of Spain will take on Dmitry Tursunov of Russia.
In men's first-round matches on Thursday, 20-year-old Australian Bernard Tomic beat French qualifier Marc Gicquel 7-5, 7-6 (7/3) to set up a second-round meeting with second-seeded Scot Andy Murray.
Results on Thursday from the third day of the $8.5 million WTA and ATP Masters Miami hardcourt tournament (x denotes seeding):
Olivier Rochus (BEL) bt Tatsuma Ito (JPN) 4-6, 6-4, 3-1 - retired
Lu Yen-Hsun (TPE) bt Robby Ginepri (USA) 7-5, 6-1
David Goffin (BEL) bt Robin Haase (NED) 7-6 (7/4), 3-6, 6-1
Guido Pella (ARG) bt Carlos Berlocq (ARG) 2-1 - retired
Guillaume Rufin (FRA) bt Marius Copil (ROM) 6-4, 4-6, 6-1
Lukasz Kubot (POL) bt Frank Dancevic (CAN) 4-6, 6-4, 6-3
Alejandro Falla (COL) bt Go Soeda (JPN) 7-5, 6-1
Daniel Gimeno (ESP) bt Denis Istomin (UZB) 6-2, 6-4
Viktor Troicki (SRB) bt Pablo Andujar (ESP) 6-2, 6-3
Jarkko Nieminen (FIN) bt David Nalbandian (ARG) 2-6, 6-4, 6-3
Ivan Dodig (CRO) bt Lukas Lacko (SVK) 4-6, 6-0, 6-4
Santiago Giraldo (COL) bt Rhyne Williams (USA) 6-2, 6-4
Bernard Tomic (AUS) bt Marc Gicquel (FRA) 7-5, 7-6 (7/3)
Simone Bolelli (ITA) bt Jesse Levine (CAN) 4-6, 6-3, 7-6 (7/4)
Aljaz Bedene (SLO) bt Benjamin Becker (GER) 6-4, 6-3
Thomaz Bellucci (BRA) bt Daniel Brands (GER) 2-6, 6-4, 6-2
Serena Williams (USA x1) bt Flavia Pennetta (ITA) 6-1, 6-1
Ayumi Morita (JPN) bt Yanina Wickmayer (BEL x31) 7-6 (7/2), 2-6, 6-3
Dominika Cibulkova (SVK x13) bt Kristina Mladenovic (FRA) 6-2, 6-3
Caroline Wozniacki (DEN x9) bt Karolina Pliskova (CZE) 5-7, 6-3, 6-3
Garbine Muguruza (ESP) bt Anastasia Pavlyuchenkova (RUS x23) 4-6, 6-2, 6-2
Li Na (CHN x5) bt Kiki Bertens (NED) 6-3, 6-1
Agnieszka Radwanska (POL x4) bt Hsieh Su-Wei (TPE) 6-3, 6-2
Magdalena Rybarikova (SVK) bt Mona Barthel (GER x27) 6-3, 7-6 (7/5)
Sloane Stephens (USA x16) bt Olga Govortsova (BLR) 0-6, 6-4, 6-4
Ajla Tomljanovic (CRO) bt Julia Goerges (GER x24) 7-6 (7/4), 6-2
Kirsten Flipkens (BEL x30) bt Stefanie Voegele (SUI) 6-4, 6-2
Petra Kvitova (CZE x7) bt Peng Shuai (CHN) 5-7, 6-2, 6-2
Andrea Petkovic (GER) bt Marion Bartoli (FRA x) 6-3, 4-1 - retired
Romina Oprandi (SUI) bt Lucie Safarova (CZE) 7-6 (7/4), 4-6, 7-6 (7/5)
Varvara Lepchenko (USA x25) bt Irina-Camelia Begu (ROM) 6-3, 6-4
Venus Williams (USA x19) bt Kimiko Date-Krum (JPN) 7-6 (7/3), 3-6, 6-4