Australian Open champion Madison Keys needed six match points as she clawed out a 6-2, 6-7 (8/10), 6-4 victory over Elise Mertens on Monday to reach the fourth round at Indian Wells.
Unable to convert two match points as she served at 5-3 in the second set, the fifth-seeded American blew two more in the tiebreaker before finally polishing off the 28th seed from Belgium in two hours and 48 minutes.
"It's always tough when you feel like you're not playing your best tennis against someone who's really tricky," Keys said. "Definitely really frustrating, lots of ups and downs.
"It's just abut surviving," added Keys, who had lost twice to Mertens since beating her at Wimbledon in 2021.
Keys is playing her first tournament since capturing her maiden Grand Slam title in Melbourne. She has found the California desert inhospitable in the past and is in the last 16 for just the third time.
She'll face either compatriot Emma Navarro or Croatia's Donna Vecic as she tries to seal a quarterfinal berth.