Ajla Tomljanovic notched the biggest upset by ranking thus far at the BNP Paribas Open, as the Australian shocked No.5 seed Garbiñe Muguruza of Spain on Saturday, 6-3, 1-6, 6-3, to reach the third round in Indian Wells.

Former World No.1 Muguruza came into the event having just won her ninth career singles title in Chicago last week, but Tomljanovic was unfazed as she collected the victory in an hour and 52 minutes.

Stat corner: World No.47 Tomljanovic, who reached her first Grand Slam quarterfinal at Wimbledon earlier this year, had previously gone 0-6 against the Top 10 this season.

But the Aussie upended that record by prevailing over 6th-ranked Muguruza, making the Indian Wells third round for the first time in her seven main-draw appearances. It marks Tomljanovic's fourth career Top 10 victory.

"I was really looking forward to playing Garbiñe, because I did lose [to her] the last couple of times," Tomljanovic said on court, following her victory. "I did try to focus on that one time I beat her, and tried to channel that energy, so I was really happy that I got through today."

Muguruza had won three of their four previous meetings, including a 59-minute dismantling in their most recent encounter at Doha last season, but Tomljanovic was able to squeak out the win despite a second-set lapse. Tomljanovic won nearly 60 percent of points returning the Muguruza first serve.

Muguruza is currently No.6 in the Porsche Race to the Akron WTA Finals, but her hopes for an imminent qualification have hit a snag with the loss. However, the Spaniard is still very much in contention to become one of the Top 8 players to contest the year-ending championships for the first time since 2017.

Key moments: The first set went Tomljanovic’s way once a string of three consecutive breaks ended with her holding a 3-2 advantage. Tomljanovic maintained that lead up to 5-3, where Muguruza let a 40-0 lead slip and lost the set with a double fault. Tomljanovic had three more winners and five fewer unforced errors than Muguruza in the opener.

However, Muguruza cleaned up her play in the second set, where the Spaniard had ten winners to just six unforced errors. Double faults crept into the Tomljanovic service games as Muguruza opened up a 4-0 lead, and at 5-1, the No.5 seed fired a deft lob to reach set point. Tomljanovic sent a forehand long on that occasion, and the match was all square.

Tomljanovic regrouped in the final set, romping to a quick break in the first game. Muguruza leveled at 3-3, but outstanding defense by Tomljanovic forced an error from the Spaniard on break point in the next game, and the Australian reclaimed her break. Tomljanovic’s rally tolerance proved stronger down the stretch, and she closed out the match with another break.

Next up: Tomljanovic will face No.26 seed Tamara Zidansek of Slovenia in the third round. Zidansek, a 2021 Roland Garros semifinalist, defeated Ana Konjuh of Croatia, 6-4, 5-7, 6-3, on Saturday.

Jabeur battles past Sevastova

Meanwhile, the woman who Muguruza beat in last week’s Chicago final, Ons Jabeur, also needed three sets to make it into the third round in Indian Wells.

No.12 seed Jabeur of Tunisia moved past Anastasija Sevastova of Latvia, 6-2, 6-7(5), 6-3, making the third round of the BNP Paribas Open for the first time in her career.

Watch the highlights: Jabeur steers past Sevastova into Indian Wells 3rd round

Despite currently sitting at her career-high ranking of World No.14, it is only Jabeur’s third main-draw appearance in Indian Wells. Nevertheless, Jabeur was able to clinch her first victory of the fortnight in just under two hours of play, for her tour-leading 45th match-win of the year.

After splitting the first two sets, Jabeur survived a five-deuce game to hold on for a 4-3 lead in the decider. The grit paid off as she attained the only service break of the set in the very next game, then held to wrap up the affair and improve to 2-1 against former World No.11 Sevastova.

Like Muguruza, Jabeur is aiming for one of the eight spots at the Akron WTA Finals in Guadalajara. The Tunisian is currently No.9 in the Porsche Race to the WTA Finals, and a solid season-ending push in her breakthrough year could put her into the year-ending extravaganza for the first time in her career.

Top seed Pliskova fends off Frech

No.1 seed Karolina Pliskova of the Czech Republic, who has already qualified for the Akron WTA Finals, picked up her first win of this year's BNP Paribas Open, easing past Polish qualifier Magdalena Frech, 7-5, 6-2.

World No.3 Pliskova has never failed to reach at least the third round in her seven career main-draw appearances in Indian Wells. She made sure to do it again with her 80-minute victory over 23-year-old Frech, who comes in at a career-high ranking of World No.106.

Big-serving Pliskova leads the WTA in aces this season, and added six on Saturday to bring her year-to-date total to 387. Pliskova converted five of her six break points on the day, helping her past a game and determined Frech.

"Credit to her, of course," Pliskova said on court after her win. "She won a couple matches, she was playing well, not really giving me any free points, which was difficult. But I think my game can be really working here pretty well. I’ve already been here for a week practicing, so hopefully I can win a couple more matches here."

Frech, in fact, claimed the first break of the day, moving ahead 4-3 in the first set. However, Pliskova charged back right away with a swift break for 4-4, and then powered her way to a 6-5 lead. In that game, a stunning rally backhand down the line gave Pliskova set point, which she converted after Frech misfired on a floater into the net.

Pliskova was less troubled in the second set as she blasted her way to a 5-1 lead, although the Czech faltered serving for the match, allowing Frech one more game. Pliskova, though, notched her fifth break of the day in the following game to seal victory.