Victoria Azarenka's renewed love affair with Melbourne Park continued as the two-time champion took just 67 minutes to steamroll 15th seed Elina Svitolina 6-0 6-2.
Meanwhile, fourth seed Krejcikova took a more scenic route, coming back from a set down to defeat fellow French Open champion Jelena Ostapenko 2-6 6-4 6-4 in two hours and 10 minutes.
Opening third round action beneath clear blue skies and a beaming sun on Rod Laver Arena, Azarenka, seeded 24th, could not have scripted a better start as she vied for a coveted place in the final 16 for the first time since 2016.
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The powerful 32-year-old pounded crisp groundstrokes to break her younger rival a trio of times in what was her first clash against a top 20 opponent at the year's first major since 2016.
The Belarusian denied Svitolina scoreboard honours by closing out the opener to love in 25 minutes as her younger rival punched a backhand wide.
Svitolina, who had lost all four of her previous battles against Azarenka, succumbed to an early break in the first game of the second set. Trailing 1-2, the Ukrainian created her first break point chance of the match, but was unravelled by a loose forehand.
In form and unflappable, Azarenka further stamped her authority on the match, guiding a backhand lob over her shorter foe's head to break for a more comfortable 5-2 lead.
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With her back against the wall, Svitolina demonstrated grit, saving four match points: the first with a deftly placed volley, the second with a stunning backhand winner, the third with a sizzling forehand winner down the line; and the fourth, thanks to Azarenka donating only her ninth unforced error of the match.
As the intensity escalated, the former world No.3 created three break-point opportunities that Azarenka shrugged off, one with an ace. On match point number five, Svitolina notched her 26th unforced error by dumping forehand into the net to hand Azarenka victory.
The Belarusian mother-of-one, who has dropped just nine games in her first three rounds, said she was pleased with her consistency and ability to dominate Svitolina.
"I wanted to put as much pressure as I could on her and kind of not let her come into the match," explained Azarenka/ "I know if I give her a little room, she's going to get back out there."
Barbora Krejcikova v Jelena Ostapenko
Next up on Rod Laver Arena, Ostapenko, renowned for her all-or-nothing style of play, snatched an early 3-1 lead by breaking her favoured opponent.
Krejcikova had a chance to break back in the seventh game, but Ostapenko kept swinging and finding her targets. Although the higher-rated Czech saved one set point with a huge first serve, the 24-year-old Ostapenko stepped in to slam a cross-court backhand winner to clinch the opening set.
Krejcikova, 26, steadied in the second, recovering from a 1-3 deficit by breaking her streaky rival not once, but twice. Serving with a 5-4 lead in the second, the right-hander sealed the set with an ace to force a decider.
In hot conditions, both players turned to ice towels to cool down. But after a nearly nine-minute bathroom break that earned Krejcikova a time violation warning, Ostapenko dropped her first service game of the third.
At 2-1, Krejcikova faced two break points in a game in which she served a pair of double faults, but fired a backhand winner to hold.
The hard-hitting Latvian, on a quest to secure her first berth in a Grand Slam fourth round since Wimbledon in 2018, had another chance to get the match back on even footing in the eighth game, but once again, was denied by Krejcikova.
Not one to go down without a fight, Ostapenko saved one match point before slapping a backhand into the net, to her Czech rival's delight.
"Today's match was really tough, really difficult, I had to really dig deep to get this win," said Krejcikova, who won just a single more point in total than Ostapenko. "She's just smashing the ball and hitting winners.
"I was really happy that I found the fighting spirit in me," added a relieved Krejcikova, who placed just 23 winners to her opponent's 40.
The fourth seed served seven double faults, a stat she will no doubt seek to improve on Sunday.
Azarenka has a slight head-to-head advantage over her next opponent, having overcome Krejcikova in their only prior singles meeting at the Ostrava Open in 2020 in three sets.
"I think the rise of Barbora has been pretty incredible over the last year and a half," said Azarenka, referencing Krejcikova's surge into the top 5 last year after ending 2020 ranked No.65.
"She can play aggressive, she can mix it up, very dangerous player."
The Czech said she's looking forward to seeing how her game fares against a player she has long admired.
"Playing Vika, it’s very special,' said Krejcikova. "I remember when I was a junior here and she was playing, she was actually winning the titles."