Miami - 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."
Results on Friday in the Miami Open WTA and ATP Masters hardcourt tournament (x-denotes seeded player):
Novak Djokovic (SRB x1) bt Bernard Tomic (AUS) 7-6 (7/2), 6-2
Federico Del Bonis (ARG) bt John Millman (AUS x32) 7-5, 3-6, 7-6 (7/2)
Roberto Bautista (ESP x22) bt Janko Tipsarevic (SRB) 7-6 (7/3), 6-4
Fabio Fognini (ITA x15) bt Guido Andreozzi (ARG) 5-7, 6-4, 6-4
Milos Raonic (CAN x12) bt Maximilian Marterer (GER) walkover
Kyle Edmund (GBR x19) bt Ilya Ivashka (BLR) 6-3, 6-2
Albert Ramos (ESP) bt Lucas Pouille (FRA x25) 4-6, 6-4, 6-3
John Isner (USA x7) bt Lorenzo Sonego (ITA) 7-6 (7/2), 7-6 (9/7)
Hubert Hurkacz (POL) bt Dominic Thiem (AUT x3) 6-4, 6-4
Felix Auger-Aliassime (CAN) bt Marton Fucsovics (HUN x29) 6-4, 4-6, 6-0
Nikoloz Basilashvili (GEO x17) bt Mischa Zverev (GER) 6-3, 6-2
Robin Haase (NED) bt Lloyd Harris (RSA x16) 3-6, 6-3, 6-4
Borna Coric (CRO x11) bt Roberto Carballes (ESP) 7-6 (9/7), 0-6, 6-2
Jeremy Chardy (FRA) bt Gilles Simon (FRA x23) 6-4, 6-2
Nick Kyrgios (AUS x27) bt Alexander Bublik (KAZ) 7-5, 6-3
Dusan Lajovic (SRB) bt Kei Nishikori (JPN x5) 2-6, 6-2, 6-3
Naomi Osaka (JPN x1) bt Yanina Wickmayer (BEL) 6-0, 6-7 (3/7), 6-1
Hsieh Su-Wei (TPE x27) bt Alison Riske (USA) 6-2, 7-5
Monica Niculescu (ROM) bt Garbine Muguruza (ESP x20) 7-6 (7/0), 4-6, 6-2
Caroline Wozniacki (DEN x13) bt Aliaksandra Sasnovich (BLR) 6-4, 6-4
Ajla Tomljanovic (AUS) bt Aryna Sabalenka (BLR x9) 6-3, 6-4
Anett Kontaveit (EST x21) bt Amanda Anisimova (USA) 6-3, 1-6, 6-4
Bianca Andreescu (CAN) bt Sofia Kenin (USA x32) 6-3, 6-3
Angelique Kerber (GER x8) bt Karolina Muchova (CZE) 3-6, 6-3, 6-3
Viktoria Kuzmova (SVK) bt Anastasia Pavlyuchenkova (RUS x31) 6-7 (5/7), 6-4, 7-5
Karolina Pliskova (CZE x5) bt Petra Martic (CRO) 6-3, 6-4
Yulia Putintseva (KAZ) bt Belinda Bencic (SUI x23) 6-3, 7-5
Anastasija Sevastova (LAT x11) bt Katerina Siniakova (CZE) 6-2, 0-6, 6-4
Elise Mertens (BEL x16) bt Pauline Parmentier (FRA) 6-2, 7-5
Marketa Vondrousova (CZE) bt Jelena Ostapenko (LAT x22) 7-5, 6-1
Tatjana Maria (GER) bt Camila Giorgi (ITA x29) 6-3, 6-4
Sloane Stephens (USA x4) bt Ons Jabeur (TUN) 6-2, 6-3
Wang Yafan (CHN) bt Elina Svitolina (UKR x6) 6-2, 6-4
Wang Qiang (CHN x18) bt Johanna Konta (GBR) 6-4, 6-0
Serena Williams (USA x10) bt Rebecca Peterson (SWE) 6-3, 1-6, 6-1
Daria Kasatkina (RUS x14) bt Cori Gauff (USA) 6-3, 6-2
Venus Williams (USA) bt Carla Suarez (ESP x24) 7-6 (7/4), 6-1
Polona Hercog (SLO) bt Misaki Doi (JPN) 7-6 (7/4), 6-4
Simona Halep (ROM x2) bt Taylor Townsend (USA) 6-1, 6-3
Danielle Collins (USA x25) bt Whitney Osuigwe (USA) 7-6 (7/3), 6-0
Alize Cornet (FRA) bt Mihaela Buzarnexcu (ROM x30) 7-6 (9/7), 6-1