World number one Iga Swiatek passed the test she'd been looking for, roaring through the tiebreaker to win a roller-coaster clash with Bianca Andreescu 6-3, 7-6 (7/1) to reach the fourth round at Indian Wells.
The victory took her a step closer to becoming just the second woman, after Martina Navratilova in 1990 and '91, to win back-to-back titles in the combined WTA and ATP Masters 1000 event.
She would go on to win the French and US Opens last year, but she got a run for her money from Canada's Andreescu, whose 2019 Indian Wells triumph was the springboard to a breakout season that included a US Open title.
After an exchange of breaks in the first two games, Swiatek saved three break points in the fifth to launch a run of three straight games that took her two a 5-2 lead.
Andreescu held to force her to serve it out, and the Pole pocketed the first set on her second set point.
Swiatek broke Andreescu to open the second set. But as the blistering baseline rallies continued the Canadian wasn't about to let her make it a runaway.
Unable to convert a break chance in the second game, Andreescu then took her turn to put together a run of games, winning four straight with two breaks of serve -- including breaking Swiatek to love for a 4-2 lead.
Undaunted, Swiatek put it back on serve in the next game and broke again for a 5-4 lead.
She couldn't serve it out, but when they got to the tiebreaker she was in complete control, winning the first four points and sealing it on her first opportunity after two hours and seven minutes -- almost twice as long as she needed for her second-round win over Claire Liu.
"Bianca can change the rhythm pretty well on this surface, it can get tough," Swiatek said. "I'm pretty happy that I was solid most of the time and I could be really composed in the tiebreaker.
"I'm even glad that I had a chance to play under pressure a little bit more and see how I'm going to cope with that."
Swiatek next faces another former US Open champion for a place in the quarter-finals, Britain's Emma Raducanu.
Raducanu, who has battled nagging wrist trouble and tonsillitis in recent weeks, dispatched big-hitting Brazilian Beatriz Haddad Maia 6-1, 2-6, 6-4.
"Honestly my goal here is to approach every match the same way, doesn't matter if it's second round or the final," Swiatek said.
"And I'm pretty sure that I got into the rhythm already so hopefully I'm going to play better and better every match.