Garbiñe Muguruza was playing as well as anyone early in the 2021 season, winning 16 of 19 matches among the Australian and Middle East swings, where she took the title in Dubai. And then, during the transition to clay, she suffered a left thigh injury.

She struggled for several months, but qualified for the Akron WTA Finals in Guadalajara as the No.5 seed. Four years after her last year-end appearance, Muguruza emerged an unlikely champion.

“I mean, it is true that the last couple of years I didn’t play the same way I played before,” she said afterward. “I’m like,`I have the tennis, I just have to show it.’ This is just another proof that I think I’m actually in the best moment of my career.”

She’s not alone.

One of the WTA’s leading storylines for 2021? The element of surprise, as a refreshing new wave of challengers made headlines. With the 2022 season rapidly approaching, that trend is likely to continue, for women’s tennis has never been deeper, more open to suggestion.

Last season the four Slam titles were won by four different players: Naomi Osaka (Australian Open), Barbora Krejcikova (Roland Garros), Ashleigh Barty (Wimbledon) and Emma Raducanu (US Open), while Belinda Bencic won the Tokyo Olympics and Muguruza the WTA Finals. In the eight WTA 1000-level events, only Barty and Aryna Sabalenka emerged as multiple champions.

Going forward, it isn’t hard to imagine a similar sharing of the wealth.

Meanwhile, six players made their Top 10 debuts: Iga Swiatek, Maria Sakkari, Paula Badosa, Anett Kontaveit, Ons Jabeur and Barbora Krejcikova. Five of them were in Guadalajara and all are 27 or younger. Sakkari, from Greece, Tunisia’s Jabeur and Kontaveit of Estonia were the first women from their countries to crack the WTA Top 10.

Read more: Barty, Krejcikova among 2021 WTA award winners

Why is this happening now?

COVID-19, of course, had a profound effect on the sport, truncating the 2020 season. Younger players might have suffered arrested development and lost the opportunity to gain traction at the higher levels. The protocols of 2020 were difficult for everyone, but it seemed some of the more established players had a difficult time adapting.

At the same time, the dominant players of recent years have been increasingly challenged by younger athletes. Of the 10 active multiple Grand Slam winners, only three – Osaka (24), Barty (25) and Muguruza (28) are under 30.

Serena Williams, now 40, won her last major nearly five years ago and has ruled herself out of the Australian Open for medical reasons. Sister Venus, 41, last won at Wimbledon in 2008 and is ranked World No.316. It’s been more than a decade since Kim Clijsters, 38, won a major. Same for Svetlana Kuznetsova. Angelique Kerber, Victoria Azarenka, Petra Kvitova and Simona Halep – who turned 30 this past fall – despite some encouraging results, are finding it more and more difficult to advance to the deep end of the Grand Slams.

Top seeds Krejcikova/Siniakova defeat Hsieh/Mertens to win WTA Finals: Highlights

The surprising results of 2021 beg a multitude of questions as a new season dawns:

After three consecutive years as the year-end World No.1, can Barty continue her reign on top? What to expect from Osaka and the Williams sisters? Will either Sabalenka or Sakkari, who both broke through with a pair of major semifinals, take it to the next level? Can Krejcikova, the WTA’s Most Improved Player, validate her phenomenal season, which included singles and doubles titles at Roland Garros and doubles victories with Katerina Siniakova at the Tokyo Olympics and WTA Finals?

How will Kontaveit’s spectacular run at the end of the season, when she won 26 of 29 matches, four titles in the span of 10 weeks and qualified for Guadalajara, translate in 2022? Similarly, can Badosa use her Indian Wells triumph as a springboard for greater things?

“Actually it’s pretty crazy when you think you’re one of the top eight players, best players, in the world,” Sakkari said in Guadalajara, perhaps speaking for the five other year-end rookies. “A few years back I wouldn’t even believe that I could be here.”

Back in 2015, Serena won the season’s first three majors and came within two matches of a calendar-year Grand Slam. Roberta Vinci defeated Serena in the US Open semifinals before losing to fellow Italian Flavia Pennetta in the final. A year later, Kerber scored bookend wins at the Australian Open and US Open.

In the five years since, no woman has won more than one major in a given year. In that time, with 19 majors played, 14 different women have won titles. By contrast, The Big Three won 17 of those majors on the men’s side, leaving only two first-time winners, Dominic Thiem and Daniil Medvedev.

Darren Carroll/USTA

The season’s final Grand Slam event provided the perfect microcosm of this breathtaking volatility – and, quite possibly, for what lies ahead.

Raducanu, who began the year ranked World No.343, won three qualifying matches at the US Open, then took out five straight Top 50 players – Zhang Shuai, Sara Sorribes Tormo, Shelby Rogers, Bencic and Sakkari – before beating fellow teenager Leylah Fernandez in the final. Fernandez, ranked World No.73 going in, was part of the first major final between two unseeded players.

At the age of 18 and playing in only her fourth tour-level event, Raducanu became the first qualifier to win a major. She finished the year ranked World No.19 and was voted the WTA’s Newcomer of the Year.

“I’ve always dreamed of winning a Grand Slam – you just say these things,” said Raducanu, who won 10 matches and all 20 sets in New York. “But to have the belief I did, and actually executing and winning a Grand Slam, I can’t believe it.”

Believe it. This is happening. The field is rich and the opportunities ripe.