Serena Williams had to survive a second-set scare at the Miami Open as the three-time defending champion moved into the third round.
Williams beat American compatriot Christina McHale 6-3 5-7 6-2, taking just over two hours to progress.
Fifth seed Simona Halep advanced with a win over Daria Kasatkina.
It was a mixed day for the rest of the seeds as Agnieszka Radwanska, Petra Kvitova and Elina Svitolina all progressed, while Lucie Safarova and Samantha Stosur were among the big-name exits.
WILLIAMS HICCUP NOT FATAL
Williams does not drop many sets at the Miami Open, so the world number one will be glad to know her recovery powers are intact after passing up a match point opportunity on the way to losing the second set against McHale.
She needed over two hours to get the job done but lives to fight another day.
Radwanska had a much better time of it as she cruised by France's Alize Cornet 6-0 6-1.
Her triumph in one hour, seven minutes saw the Pole win 77 per cent of points on her first serve.
Halep beat Kasatkina 6-3 7-5 in a relatively comfortable performance, to ensure the day's top three seeds progressed.
PETKOVIC, SAFAROVA KNOCKED OUT
Six seeds were knocked out of the Miami Open on Thursday, with 11th seed Safarova the highest ranked of them.
She went down 6-2 6-3 Yanina Wickmayer, while 21st seed Andrea Petkovic lost 7-6 (7-5) 3-6 7-6 (7-2) to Caroline Garcia.
Sloane Stephens (20) lost to Heather Watson 6-3 6-0, while Stosur lost to Julia Goerges in three sets.
The other seeds to exit were Daria Gavrilova and Anna Karolina Schmiedlova.
WINNERS ARE GRINNERS
Halep's win over Kasatkina was her 10th at the Miami Open, but that achievement pales in comparison to Williams' 19th-straight victory at the tournament.
You have to go all the way back to the 2012 quarter-finals at this tournament to find her last loss.
Williams was more than tested by McHale, who showed tremendous grit to save 12 of the 17 break points she faced.
WILLIAMS IMPRESSED BY MCHALE
Williams was suitably impressed by what she saw from McHale and was full of praise for her fellow American, saying: "She can, should and will be very proud of herself in this match. I think it can also show her how good she is."
Meanwhile, Angelique Kerber is looking forward to her return, saying: "It feels good to be back in Miami. I'm feeling good again. I really enjoyed the win in Australia, I had a bit of time to rest and now I'm working hard again."
KERBER BACK IN ACTION
Second seed Kerber will start her campaign with a match against Barbora Strycova, while Venus Williams is playing Elena Vesnina.
Elsewhere, fourth seed Garbine Muguruza takes on Dominika Cibulkova.