After a two-and-a-half-year hiatus, the BNP Paribas Open returns to the tennis calendar in style with a packed slate of intriguing first-round tilts. Here are seven to circle in Day 1's order of play.

Kaia Kanepi (EST) vs. Madison Keys (USA)

Two of the biggest hitters in the draw go toe-to-toe off the bat. Seeing former World No.7 Keys as an unseeded floater is still novel: the American's 2021 record is just 10-14, and last month she dropped out of the Top 50 for the first time since first entering it in July 2013. Keys, currently ranked back at No.50, will be seeking to snap a six-match losing streak dating back to Wimbledon.

Kanepi, on the other hand, is very much used to lurking in draws. The 36-year-old plays a pared-back and idiosyncratic schedule these days, often choosing to prepare for Grand Slams and WTA 1000 tournaments by dropping down to ITF level - since Wimbledon, Kanepi has won ITF W25 tournaments in Parnu and Fort Worth. But she's still just as capable of springing an upset of a big name. This year, the World No.60 has scored wins over Aryna Sabalenka, Sofia Kenin and Yulia Putintseva.

The pair have split two previous meetings, with Kanepi winning 6-4, 6-3 in the first round of Madrid 2015 and Keys triumphing 6-3, 6-3 in the 2017 US Open quarterfinals. Curiously, Indian Wells is the only North American tournament at WTA 1000 level or above at which Keys has yet to reach the quarterfinals - her career-best performance here was a fourth-round run in 2017.

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sloane stephens
USA
More Head to Head
37.5% Win 3
- Matches Played
62.5% Win 5
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heather watson
GBR

Sloane Stephens (USA) vs. Heather Watson (GBR)

The point of note in this match is the head-to-head. Watson has long been a surprising thorn in former World No.3 Stephens' side: she won the pair's first four meetings between 2010 and 2015, and leads the overall series 5-2. That includes all four of their hardcourt meetings.

However, they have not played in over five years, since Watson's 6-3, 6-0 demolition of Stephens in the second round of Miami 2016. Much has happened since then, not least Stephens becoming a Grand Slam champion at the 2017 US Open.

Curiously, this meeting will mark the first time since their first pro encounter, at the 2010 Toronto ITF W50 event, that Watson has been the higher-ranked of the two, perched at No.57 to Stephens' No.73. Yet in terms of recent form, the American has the edge. After losing five of her first six matches this year, Stephens' record since Miami is 17-11. Even some of her recent defeats - to Danielle Collins in San Jose, Aryna Sabalenka in Montréal and Angelique Kerber at the US Open - were still notable for the high quality on show.

By contrast, Watson has had a lean 2021, winning just seven WTA main draw matches so far, and will be seeking to snap a four-match losing streak.

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2021 Budapest

Andrea Petkovic (GER) vs. Yulia Putintseva (KAZ)

Another pair of old rivals, Petkovic and Putintseva will face each other for the sixth time back at the site of their first encounter. In 2013, Petkovic routed an 18-year-old Putintseva 6-0, 6-2 in the first round of Indian Wells qualifying.

Both have rounded into form over the second half of 2021. Putintseva, whose penchant for marathon matches and epic rallies filled with hot shots makes her one of the Tour's best value-for-money players on a weekly basis, has been translating that into impressive results lately. A second career title in Budapest in July was followed by a run to the Nur-Sultan final on home soil last week.

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andrea petkovic
GER
More Head to Head
33.3% Win 2
- Matches Played
66.7% Win 4
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yulia putintseva
KAZ

Meanwhile, Petkovic started the year with a paltry 4-11 record through June, and has admitted: "I was ready to retire, I almost did retire - I started five new jobs!"

A runner-up showing in Hamburg, where she was the inaugural tournament ambassador, rejuvenated the German's year, and she followed that with her first title in six years in Cluj-Napoca. In three months, she has risen from World No.130 to World No.74.

Putintseva leads the overall head-to-head 3-2, though Petkovic was a 6-2, 1-6, 6-4 victor on clay in Hamburg three months ago. They have not played on hard courts since that first Indian Wells meeting eight years ago.

[Q] Mai Hontama (JPN) vs. [LL] Jasmine Paolini (ITA)

This year's qualifying rounds have delivered a clash between two rising players in recent hot form. Hontama, 22, had an eye-catching breakout run last week in Chicago: the Japanese player qualified for her WTA main draw debut, then upset Caroline Garcia and Shelby Rogers en route to the quarterfinals.

In those matches and her ultimate loss to eventual champion Garbiñe Muguruza, Hontama consistently impressed with her ability to take the ball early and turn defence into attack. This week, she has backed up that performance with solid qualifying wins over Panna Udvardy and Kristina Kucova.

Paolini had a big-stage moment at the US Open, when she thrilled the Louis Armstrong Stadium crowd by stretching Victoria Azarenka in a pulsating 6-3, 7-6(1) second-round loss. The Italian backed that up by winning her maiden title in Portoroz last month, though surprisingly fell to Kateryna Kozlova in the final round of qualifying this week. She defeated Hontama 6-2, 6-2 in their only previous meeting, in the first round of the 2019 Tokyo ITF W100 event.

Maria Camila Osorio Serrano (COL) vs. Aliaksandra Sasnovich (BLR)

Osorio Serrano, 19, was one of the breakthrough young stars of the first half of 2021. The Colombian teenager won her first title on home soil in Bogota, and backed that up with semifinal runs in Charleston and Belgrade and a third-round showing as a qualifier at Wimbledon.

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The World No.71's all-court grit should make for a fine stylistic contrast against World No.100 Sasnovich's flat hitting in a rematch of their Belgrade quarterfinal in May, which Osorio Serrano won 6-4, 6-2. But another reason to pay attention to this clash will be what comes next: the winner will earn a second-round date with No.17 seed Emma Raducanu, in the British teenager's first match since winning the US Open.

Marta Kostyuk (UKR) vs. Zhang Shuai (CHN)

Just two months ago, Kostyuk was the leader of the 2002-born generation. That was until Emma Raducanu, Leylah Fernandez and Clara Tauson all overtook her in swift succession with star turns. How will the talented Kostyuk, the first to break through of her peer group, respond? The Ukrainian World No.58 has tailed off after a strong start to the year. Since reaching the fourth round of Roland Garros, her main draw record has been just 4-6.

However Kostyuk, 18, did manage to score a 4-6, 6-4, 6-0 win over Zhang in Eastbourne qualifying. The Chinese player has rebounded well recently after losing nine of her first 10 matches of 2021 - though in recent weeks her success has mostly been on the doubles court. Zhang won her second Grand Slam trophy at the US Open with Samantha Stosur, and followed that by partnering Sania Mirza to the Ostrava title.

[Q] Elena-Gabriela Ruse (ROU) vs. Alizé Cornet (FRA)

Ruse, the newest entrant to the Top 100, has had an impressive surge over the past three months. The powerful Romanian has been bubbling under Tour level for several years, but put it all together in July to win her first WTA title as a qualifier in Hamburg. Nor did she stop there - in her very next tournament, again as a qualifier, she was runner-up in Palermo.

Now ranked No.92, Ruse has translated her form impressively to her first North American hardcourt tournaments, qualifying for the US Open and reaching the third round of Chicago last week. A clash against the wily veteran Cornet should be a demonstrative affair.

The winner will also set a popcorn second-round match against No.23 seed Leylah Fernandez, in the Canadian teenager's first match since the US Open final.

Click here for the full Day 1 Order of Play.