The Biggest Tennis Storylines to Watch at the Start of 2017

Roger Federer returns, Serena Williams chases history and the Andy Murray and Novak Djokovic rivalry heats up. Those are just three of the top storylines to watch in early 2017. 

With the Brisbane International and the start of the new tennis season just days away, all eyes will be focused on the return of big stars to the court—it's been nearly six months since tennis icons Federer and Williams have played in an official match. 

Federer and Williams continue to defy Father Time as the two 35-year-olds remain serious Grand Slam title contenders. Williams, however, will seek to become the sole owner of the record for most Slams won in the Open Era. 

Meanwhile, Murray and Djokovic are still recovering from an epic end to the 2016 season. Murray defeated Djokovic at the ATP World Tour Finals in London to take the title and the No. 1 ranking. The battle for No. 1 rolls into 2017.

There will be noticeable absences at this year's Australian Open. Maria Sharapova is still serving a suspension for a banned substance. Victoria Azarenka just gave birth to her first child. Madison Keys is out with an injury, and Juan Martin del Potro, last year's Comeback Player of the Year, announced Monday that he has withdrawn from the Auckland Classic and Australian Open. 

Still, there are plenty of talking points ahead of the new season. The following are the top storylines to watch at the beginning of 2017. 

The Red-Hot Andy Murray and Novak Djokovic Rivalry

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Andy Murray and Novak Djokovic hug after the 2016 ATP World Tour Finals in London.

Right out of the gates, Murray has to prove himself. Although he got the best of Djokovic at the ATP Would Tour Finals, the Serb still leads the head-to-head, 24-11. 

Was Murray's late-season surge a fluke? Did he benefit from an injured and fatigued Djokovic? Or has Murray changed more than momentum in this rivalry?

Those questions will keep this battle in the spotlight. 

Federer told reporters that he expects Djokovic to reclaim the No. 1 ranking at some point: "It’ll be hard in the next few months because of the sheer domination he had at the beginning of this year, so I think Andy will hang on to it for a while. But then again, we have to see who stays injury-free. That plays a lot into it as well." 

Serena Williams' Run on the Record Books

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Serena Williams poses with the singles and doubles championship trophies at Wimbledon 2016.

No longer No. 1, Williams enters the new year chasing Angelique Kerber.

Of course, Williams would love to get back to No. 1, but her eyes are set on a bigger prize: the record for most Grand Slam titles ever. Williams is tied with Steffi Graf on 22 Grand Slam titles.

She'd love to take the record at the Australian Open and spend the rest of the year floating on a pressureless high.

In December, Williams posted a picture of her skirt at the U.S. Open on her Instagram (h/t ESPN.com's D'Arcy Maine) with the caption, "I'm ready to twirl into next year." 

Nick Kyrgios' Attitude Adjustment

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Nick Kyrgios has a discussion with the chair umpire during a changeover at the 2016 Shanghai Masters.

Nick Kyrgios is coming off a recent three-week ban for unsportsmanlike conduct during the Shanghai Masters.

Can he stay out of trouble long enough to capitalize on his career-high ranking at No. 13?

Kyrgios' maturity will be under scrutiny and a hot topic early in 2017, especially with the season kicking off Down Under, his neck of the woods. 

His initial suspension was eight weeks, but the ATP reduced it when Kyrgios agreed to see a sports psychologist.

"I've been doing that (seeing a psychologist), and it's actually been good," Kyrgios told the Australian Associated Press (via ESPN).

Kyrgios is scheduled to compete in the Hopman Cup at the start of January, along with friend Alexander Zverev.

Zverev told Perth Now's Bridget Lacy: "Off-court he (Kyrgios) is one of the nicest guys on tour, and we get along well and keep in touch all the time, so I have nothing bad to say against him."

Angelique Kerber's Reign at the Top

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Angelique Kerber celebrates new No. 1 ranking and U.S. Open title back in Germany.

Kerber reached No. 1 in part because of Williams' scaled-back schedule over the past two seasons. Over that time, Kerber has played in twice as many tournaments as Williams. 

Still, Kerber outperformed Williams at the Australian Open and U.S. Open and was the best player last year. Can she maintain the same focus and level of play in 2017?

Despite losing to Dominika Cibulkova in the final of the WTA Tour Finals, Kerber was able to finish the year ranked No. 1. That, and the two Grand Slam titles, should give her confidence going in to 2017.

The Coaching Carousel

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Boris Becker looks on during the 2016 ATP World Tour Finals in London.

Boris Becker is the biggest coaching casualty from 2016. However, his split with Djokovic is hardly the only major coaching change.

Rafael Nadal brought in Carlos Moya, who was part of Milos Raonic's team. Madison Keys is back with Lindsay Davenport after parting ways with Thomas Hogstedt, who's now back with Eugenie Bouchard.

After a career-best season, Johanna Konta also split with her coach, Esteban Carril. She's working with Azarenka's former coach, Wim Fissette, on a trial basis. 

Karolina Pliskova upset Williams to reach the U.S. Open final in the highlight of a breakout season. So, of course, she has fired her coach and picked up Petra Kvitova's former coach, David Kotyza. 

Pam Shriver told ESPN.com's Peter Bodo: "Today's players can't seem to find a coaching match, and that's a real problem. Madison Keys, Sloane Stephens, Eugenie Bouchard. You cannot have that many [coaches]. I think it's a little bit of our instant gratification; nobody has the patience in this day and age."

Rested Roger Federer Returns

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Roger Federer hits a forehand during a match at Wimbledon, 2016.

Federer told the ATP that he feels rested after recovering from a knee injury. But the proof will be in the performance. 

"Maybe, mentally, I needed this more than I thought I would,” Federer told reporters, per Charlie Eccleshare of the Telegraph. “Maybe my body needed this more than I thought.”

He'll find the ATP landscape pretty much in the place he left it, with Murray and Djokovic battling for No. 1 and Nadal trying to recapture his championship form. 

The only difference might be that younger players like Zverev (19), Dominic Thiem (23) and Kyrgios (21) have moved from up-and-coming to solid top-20 players. 

How Federer starts the year might determine if he's going to have a successful comeback or another setback.