Serena Williams survived an "irresponsible" second set lapse on Friday to see off Sweden's Rebecca Peterson 6-3, 1-6, 6-1 in her second-round opener of the WTA and ATP Miami Open.
"I wasn't really happy with my performance," admitted the 23-time Grand Slam champion, who is playing in just her third tournament of 2019 having lost in the Australian Open quarter-finals before retiring in the second set of her third-round match against Garbine Muguruza with a viral illness at Indian Wells last week.
"Had to take a lot of time off the last week," she said. "It's definitely not easy at all. But I'm through it. That's that. I've just got to get my game back to where I know it can be.
"I told myself at the end of the second set that I could not lose this match.
"I knew that I could play a lot, lot, lot better. I just had to be better. At this point it was irresponsible to be playing the way I was playing in the second set."
Williams, an eight time winner in Miami, was just relieved to make it through to the third round where she will meet China?s Wang Qiang who thrashed Britain's Jo Konta, the 2017 Miami Open champion, 6-4 6-0.
The former world number one was certainly rusty in her first ever match against the 63rd-ranked Swede, despite starting strongly and easing into a first set lead.
Peterson, however, who lost in the first round in Indian Wells, produced some excellent tennis in the second and managed to break down Williams's serve to take the match into a deciding set.
As the South Florida sun began to lower, Williams appeared to struggle with her ball toss.
"It was interesting, because first of all it was dark out there, which was really odd," Williams said. "I wasn't sure if there should be lights. The shadow was so intense it was actually dark.
"Then there was light, but only on my side. That was weird because I literally couldn't see.
"But I need to just move on and really focus on playing better or not being in the tournament much longer."
Williams, 37, is still seeking a first title since the birth of daughter Alexis Olympia.
She admitted it was sometimes hard to stay patient, although she believes returning to the top 10 after her extended maternity leave qualifies as "extremely successful".
"It's just a step at a time," she said. "Just because my level of success is so much higher than what's natural, I have to take these moments and say, 'You're doing great,' encourage myself in a positive way so I can get that success that I want to have since coming back from the baby."