5 storylines to watch at the 2021 Australian Open

The 2021 tennis season is officially underway with Australian Open tuneup events taking place in Melbourne.

COVID-19 has dramatically altered the lead-up to the first Grand Slam, though tournament director Craig Tiley is adamant the event will go on as scheduled.

Here are five storylines to watch when the action begins Sunday evening.

How will COVID-19 impact the tournament?

The Australian Open was the only Grand Slam unaffected by the coronavirus pandemic last year. However, COVID-19 looms large as the 2021 edition nears. The major was pushed back three weeks from its original start date to allow players to travel and then quarantine for two weeks before competing.

Despite Tennis Australia exercising caution, a worker at one of the designated tournament hotels tested positive for the virus, prompting players to self-isolate and the Australian Open to postpone play Thursday at all six tuneup events.

How will Tennis Australia respond if a player or member of their inner circle contracts COVID-19? The country has taken strict measures to combat the virus, so nothing is off of the table.

Serena goes for No. 24

Serena Williams resumes her pursuit of an elusive 24th Grand Slam singles title. The American legend trails Margaret Court by one major championship for the sport's all-time lead and has come agonizingly close over the last three years.

Williams has fallen in straight sets in each of her last four Grand Slam final appearances. The 39-year-old criticized her performance after losing to Bianca Andreescu in the 2019 US Open final, calling her play "inexcusable." Some retired pros blamed nerves for Williams' dip in form during her most recent championship matches.

"I don't know if it's just that she wants to win one so badly after (her daughter) Olympia was born or that she is going for the all-time Slams record," former World No. 1 Andy Roddick told theScore in 2019. "Whatever the reasons are, I think she really wants it, and I think there's probably such a thing as wanting it too badly."

All eyes will be on Williams as she chases history once again. Can she finally exorcise her recent Grand Slam demons?

Will Rafa pass Roger?

Williams isn't the only player on the cusp of an extraordinary accomplishment.

Rafael Nadal can surpass Roger Federer for the most Grand Slam singles titles by a male player with a championship in Melbourne. Although the Spaniard only has one Aussie Open title on his loaded resume, he's reached the men's final four times since his lone triumph in 2009.

Nadal's dominance on clay is well-documented, but his hard-court success is sometimes overlooked. Twenty-two of Nadal's 86 career singles titles have come on the hard court, including five Grand Slams and 10 Masters 1000 crowns.

The world No. 2 has reached the Australian Open quarterfinals in 12 of his past 13 tournament appearances and is primed for another deep run Down Under.

Djokovic's home away from home

No male player has had more success at the Australian Open than Novak Djokovic. The world No. 1 captured a record eighth men's singles title at last year's tournament and is seeking his second three-peat Down Under. He's a perfect 8-0 in finals, including three straight-set victories.

Djokovic has won 90% of his matches at the season's first major and has been ousted before the fourth round only once over his last 14 appearances. He'll have some added confidence heading into the Australian Open having topped Alexander Zverev and Denis Shapovalov in a pair of hard-fought matches at the ATP Cup.

How will Barty, Andreescu fare after extended layoffs?

World No. 1 Ashleigh Barty returned from an 11-month hiatus last weekend, falling 3-6, 6-1, 10-8 in an exhibition matchup against two-time major champ Simona Halep. The 24-year-old competed at the Qatar Open last February before sitting out the remainder of the abbreviated 2020 campaign due to the COVID-19 pandemic.

It's been 43 years since an Aussie captured the singles title in Melbourne, but the hometown pressure didn't seem to faze Barty last year. She was the first Australian woman to enter the Happy Slam atop the WTA rankings and wound up reaching the semifinals. Repeating the same feat - if not better - is a tall task, but Barty had strong stretches of play during this week's Yarra Valley Classic.

Meanwhile, Andreescu won't have any warmup matches ahead of this season's first Grand Slam. The Canadian recently withdrew from the Grampians Trophy and hasn't played competitively since suffering a knee injury in the group stage of the 2019 WTA Finals.

Andreescu hasn't let extended layoffs affect her in the past. The 20-year-old stormed to the 2019 Rogers Cup title, defeating Williams, Sofia Kenin, Karolina Pliskova, and Kiki Bertens following a shoulder injury that kept her sidelined for the large part of five months.

Andreescu's power and variety are a threat on any court surface, and she knows what it takes to win a major.