Seven-time Grand Slam champion Venus Williams was one of four Americans to book a spot in the second round of the Yarra Valley Classic on Sunday's opening day of action from the WTA 500 event.

“It’s awesome to be back, I love Australia, it’s a beautiful moment,” Williams said, after playing her first match since Roland Garros - a 6-1, 6-3 win over Arantxa Rus of the Netherlands.

“It’s so hard to play the first match of the season, and I just think that maybe I just handled the nerves a little bit better.

“It’s not easy. Of course, I have a lot of experience, and I think that helps. Just trying to get my feet wet, trying to compete here, and feel good about what I'm doing.”

In their sole previous match, Williams defeated Rus in straight sets at the 2018 Billie Jean King Cup, which just so happened to be the American legend’s 1,000th professional match. While no such numerical significance accompanied their rematch in Melbourne, Williams once again prevailed, this time in a touch more than an hour of play.

The former World No.1, the oldest player in the draw at age 40, never dropped serve during a precise encounter, striking 18 winners to 18 unforced errors.

Her victory sets up an eye-catching second round against World No.9 and two-time Wimbledon champion Petra Kvitova of the Czech Republic.

To kick off the day, Australian Open semifinalist Danielle Collins needed just 75 minutes to secure her first victory of 2021 on Sunday at Melbourne Park - a 6-3, 6-3 triumph over Belgian Ysaline Bonaventure.

Again returning to the site of her best career major run, which saw her upset former champion Angelique Kerber en route to reaching the final four in 2019, Collins faced little adversity against the World No.123, breaking serve twice in each set to advance to the second round.

The World No.46 was absent from the first tournament of the 2021 season in Abu Dhabi, having last reached the quarterfinals at the French Open in the fall.

As the No.13 seed, Collins is one of a trio of Americans amongst the Top 16 in this draw - joining No.2 seed Sofia Kenin and No.5 seed Serena Williams. 

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2021 Yarra Valley Classic Highlights: Collins ousts Bonaventure

Collins' victory led the slate of matches for her compatriots on the first day of action at the tournament, which saw Shelby Rogers join her in the second round thanks to a 6-2, 7-5 victory over No.12 seed Fiona Ferro, the first seed to fall.

The two-time Grand Slam quarterfinalist, who won 16 of the first 17 points of the match to sprint out to a 4-0 lead, later rallied from 5-1 down in the second set to secure a two-set win.

Despite the deficit, Rogers never had to save a set point.

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A hat trick of victories for the stars and stripes was not to be in the day session, however - as former World No.11 Anastasija Sevastova proved too strong for Madison Brengle, securing a 6-4, 6-2 victory in just 65 minutes.

However, joining Williams as a late day victor was Jessica Pegula, who also secured an upset against a seeded player with a 6-4, 6-1 win over No.15 seed Kristina Mladenovic.

Bolsova safely through in straights, Gracheva wins first three-setter

Another player who had a breakthrough Grand Slam run in 2019 - Spain's Aliona Bolsova - was also among Sunday's early winners in the Yarra Valley event.

Bolsova, who reached the fourth round of the French Open as a qualifier that season, surrendered just three games in defeating India's Ankita Raina, 6-3, 6-0.

Bolsova will next face No.16 seed Marie Bouzkova of the Czech Republic, who dampened home spirits a touch thanks to a 6-2, 6-0 win over former US Open champion Samantha Stosur, who was contesting her first match in over a year.

Stosur, who became a mother during the COVID-19 hiatus last year, struggled to find her rhythm in her competitive return, with the 22-year-old Czech winning the last 10 games of the match from 2-2 in the opening set. The Aussie was broken five times and never managed to earn a break point herself. 

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Quote me on that: Daria Gavrilova charms in home return

Former Top 20 player Daria Gavrilova had a tough choice to make ahead of her opening round match: a good night's sleep, or a little celebration.

But after easing past Slovakia's Viktoria Kuzmova in little more than an hour on Margaret Court Arena, 6-2, 6-0, it seems like she made the right one.

"Last night... unfortunately, I had to miss my friend Greg's birthday. We were meant to go to karaoke. Happy birthday Greg, [but] I'm not going to sing - it's better for everyone!"

- Daria Gavrilova, on-court after her win

The win was Gavrilova's first match on home soil since 2019, following an injury layoff that lasted a full year, and she's a wildcard in this week's draw.

Having returned to WTA level at the French Open last fall, the 26-year-old currently owns a ranking of World No.451, but has a much finer pedigree than that number suggests. 

Up next for the returning Aussie? A meeting with 23-time Grand Slam champion Serena Williams.

And when prompted by the on-court interviewer for her thoughts on her next match, Gavrilova's quick wit again shone through.

"I've seen her training on Instagram," she said with a grin. "She doesn't look rusty at all."

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Pliskova, Serena headline Monday's slate

Top 5 seeds Karolina Pliskova and Serena Williams are among those set to play second round matches on Monday after having received first-round byes. Also in action are No.9 seed Donna Vekic, No.11 seed Anastasia Pavlyuchenkova and No.14 seed Nadia Podoroska.

Click here for Monday's order of play at Melbourne Park, consisting of matches from both the Yarra Valley Classic and the Gippsland Trophy.