Top seed Serena Williams needed two-and-a-half hours to eliminate Caroline Garcia 6-4 4-6 6-4.
A succession of long rallies left Williams grunting, stumbling, lunging, squealing, flailing her arms and scolding herself.
Despite all the drama and trauma, she moved one round closer to a record seventh Key Biscayne title. Williams is playing in her first tournament after a month-long layoff, and rustiness may explain her 41 unforced errors, including seven double-faults. And the 20-year-old Garcia kept Williams on her heels with deep groundstrokes and serves that topped out at 117 mph.
"I can play a hundred times better," Williams said. "I really gave myself a tremendous amount of trouble out there. Granted she played great, but I made 40-something errors. It's not the way to play professional tennis. Maybe amateur."
One point from victory, Maria Sharapova chased after a shot in the corner but couldn't reach it, so she had to keep playing.
Nearly an hour later she was still at it, trying to win that elusive clinching point against stubborn Lucie Safarova.
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Sharapova needed nine match points before she finally closed out a win Saturday night in the third round of the Miami Masters, beating Safarova 6-4 6-7(7) 6-2.