Monday was a banner day for those who had played the qualifying rounds at the WTA 500 Adelaide International. On the first day of main-draw action, qualifiers Anastasia Pavlyuchenkova and Anna Kalinskaya both recorded upsets of Top 5 seeds, before lucky loser Bernarda Pera halted Paula Badosa's comeback from injury in the first round.

Pavlyuchenkova, the 2021 Roland Garros finalist, took 1 hour and 34 minutes to oust No.5 seed Beatriz Haddad Maia 6-3, 6-4 in the tournament's opening Centre Court match.

Kalinskaya followed by winning a 7-5, 3-6, 7-5 squeaker over No.4 seed Barbora Krejcikova. Kalinskaya improves to 2-0 over Krejcikova, having already beaten the 2021 Roland Garros champion at Guadalajara in 2022.

Rounding out Centre Court action, Pera came from a set down, then 3-1 down in the third set, to take out wild card Badosa. The Spaniard was playing her first match since Wimbledon, having been sidelined by a stress fracture in her back.

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"I hit some amazing shots, to be honest," said Pera with a grin in her on-court interview.

The No.69-ranked American wasn't wrong. She struck 36 winners overall, and enjoyed purple patches in the second and third sets where she could do no wrong.

Ahead of the tournament, former World No.2 Badosa had declared herself injury-free and hungry to take the court again. The Spaniard showed little sign of rust in an impeccable first set, in which she slammed 14 of her 28 total winners. Conversely, Pera leaked 10 unforced errors to only five winners in the opener.

But two-time WTA titlist Pera's powerful game clicked into gear in the second set. A series of forehand scorchers down the line enabled her to leap out to a quick lead, while her crosscourt backhand joined the party as she closed the set out.

After missing an early pair of break points at the start of the third set, Pera dropped serve in a flurry of errors to go down 3-1 in the decider. But she gathered herself for another run of form to rattle off the last five games of the match in a blaze of swashbuckling drive volleys.

Despite the loss, Badosa can take positives from the quality of her first match in over six months. The World No.74 ended the contest with a positive ratio of 28 winners, including six aces, to 17 unforced errors, and managed to save 12 out of the 17 break points she faced.

Pera -- who had bounced back from a loss to Katerina Siniakova in the final round of qualifying -- will next face compatriot and No.2 seed Jessica Pegula in the second round.

Pavlyuchenkova defeats Haddad Maia for second time in four months

"I know [Haddad Maia is] a great fighter, and if you give her a little bit of a chance to come back-- and she kind of started to do that in the second set," Pavlyuchenkova said on court after her win. "So I knew I had to be 200 percent against her, and I’m happy it worked."

Highlights: Pavlyuchenkova def. Haddad Maia

The 32-year-old Pavlyuchenkova is currently ranked No.59 after a comeback season in 2023. The former World No.11 played only three events in 2022 due to injuries, but she came back strong last year, with a run to her third career Roland Garros quarterfinal among her highlights.

Pavlyuchenkova is now 2-0 over current World No.11 Haddad Maia, having also won on the hard courts of Hong Kong at the end of last season. Pavlyuchenkova's 26 winners in the match doubled Haddad Maia's 13, leading to the 73rd Top 20 win of her lengthy career.

Kalinskaya overhauls Krejcikova in nearly three hours

World No.75 Kalinskaya took a grueling 2 hours and 52 minutes to subdue 10th-ranked Krejcikova on Monday and garner the fourth Top 10 win of her career. 

Highlights: Kalinskaya def. Krejcikova

"It was a great match, [Krejcikova is] a very good fighter," Kalinskaya said afterwards. "She plays incredible tennis, she knows how to hit every shot, she made the match very complicated. I'm happy that I won, and I'm happy to be getting back in shape and to play better tennis every day."

After splitting the first two sets, Krejcikova broke Kalinskaya in the opening game of the third set with a winning volley, en route to a 3-1 lead. But Kalinskaya pulled back on serve at 3-3, then later saved a break point in a crucial four-deuce hold for 6-5.

In the following game, Kalinskaya cracked a powerful backhand service return to force an error on her third match point and collect the upset victory.