Serena Williams' bid for a ninth Miami Open championship got off to a stuttering start Friday.
Williams, the tournament's 10th seed, was pushed before emerging with a 6-3, 1-6, 6-1 second-round win over Sweden's Rebecca Peterson in Miami Gardens, Fla.
The event's top 32 seeds received first-round byes.
Williams most recently was the Miami champion when she three-peated with titles in 2013, 2014 and 2015. On Friday, she played her first match since an illness forced her to retire in the third round a week ago at Indian Wells, Calif.
"I could not lose this match," Williams said Friday. "I knew that I could play a lot, lot, lot better. I just had to be better. That determination was, I cannot lose this match just really kicked in. 'What do I need to do to win this match?'"
Williams' ratio of 27 winners to 23 unforced errors was superior to Peterson's 15 winners and 18 unforced errors.
"I'm not really thinking about my match too much today," Williams said. "I wasn't really happy with my performance. I had to take a lot of time off the last week.
"It's definitely not easy at all, but I'm through it. That's that. I just got to get my game back to where I know it can be."
Williams' older sister, Venus Williams, had an easier time in her second-round match, beating 24th-seeded Spaniard Carla Suarez Navarro 7-6 (4), 6-1.
Top-seeded Naomi Osaka of Japan had an up-and-down win over Belgian qualifier Yanina Wickmayer, 6-0, 6-7 (3), 6-1.
"It's the first match I've played here (at the Miami Open's new facility)," Osaka said. "I wasn't able to defend (my title) in Indian Wells, so of course I really want to do well here. I think it was all of that combination. ...
"It was really hard for me, I think, emotionally in the second set because I just started thinking about winning, not exactly the things I could do in order to win. So, yeah, I had a bit of a dip. She was also playing really well. I think between the second and third set I tried to breathe and regroup."
Other winners Friday included second-seeded Romanian Simona Halep, fourth-seeded American Sloane Stephens, fifth-seeded Czech Karolina Pliskova and eighth-seeded German Angelique Kerber.
Yafan Wang of China knocked out sixth-seeded Elina Svitolina of Ukraine 6-2, 6-4, and Ajla Tomljanovic of Australia upset ninth-seeded Aryna Sabalenka of Belarus 6-3, 6-4.
--Field Level Media