Less than two hours after Williams' withdrawal, Naomi Osaka also crashed out after Hsieh Su-wei of Chinese Taipei put on another strong performance beating the world number one 4-6, 7-6 (7/4), 6-3.
"I am disappointed to withdraw", she said in a statement.
The 23-time Grand Slam victor was set to face Wang Qiang in the last 32 but the Chinese player will progress with a bye, having beaten British No 1 Johanna Konta in the second round.
Serena Williams made another sudden tournament exit, this time blaming a previously undisclosed left knee injury. It was an wonderful experience to play at the Hard Rock Stadium this year and would like to thank the Miami Open for putting on an unbelievable event,"the Women's Tennis Association (WTA) quoted Williams as saying". Women's Tennis Association had no information on how she became injured, either.
Williams, who lives just short drive up I-95 in Palm Beach Gardens, was seeded No. 10. The 21-year-old's rank could be in jeopardy depending on who wins the tournament.
Serena Williams starts her campaign in Miami with a tight win over the world no. 63 Rebecca Peterson.
Williams, 37, has played only eight matches this year. I thought I played pretty decent compared to how much I'd been able to practice.
In the second set, Serena disappeared to lose 5 consecutive games and the set (from 1-1 to 1-6).
"I've never really seen him play live matches so I watched some video to get an idea about him", Federer said. She wasn't scheduled to play Saturday.
"This was a very emotional win for me", said Hsieh, whose 39 winners were one less than her opponent. I knew that I could play a lot, lot, lot better. Her last title was at the 2017 Australian Open before she took an extended maternity leave later that year.
Williams' stay at the Miami Open was also brief past year, when she lost in the first round to Osaka.
In her first tournament since then, at Indian Wells this month, she defeated former world No. 1 Victoria Azarenka in her opening match but then retired while trailing against another former No. 1, Garbine Muguruza, with a viral illness.
"It was interesting, because first of all it was dark out there, which was really odd", Williams said.