Early Look at Tennis' Top Storylines for the 2015 Season

The new year will be welcomed in by the sound of Andy Murray's gears turning in preparation for a step into the relative unknown. This will be just one of the top tennis storylines to look out for in 2015.

Murray will hope to be anything but tentative following a shake-up of his coaching team that has seen Dani Vallverdu and Jez Green depart.

Milos Raonic, Grigor Dimitrov and Kei Nishikori will look to distance themselves from talk of what they might be capable of and produce something substantial to stand behind. At this moment, perhaps it is Nishikori who is best placed to do so.

Stars-in-the-making Caroline Garcia, Belinda Bencic and Garbine Muguruza were among those to shine a light on the future of the WTA with individual successes last year. All three could have big years.

The following slides will establish the storylines to watch intently over the next 12 months in both the ATP and WTA Tours.

How Will the Pretenders to the Top Fare?

Michel Euler/Associated Press

Wimbledon 2014 may well prove to be the blueprint for those select few with genuine aspirations to reach inside the top 3's bubble.

Semi-final berths for Dimitrov and Raonic lit the All England Club in a refreshing hue before Novak Djokovic and Roger Federer restored normal service.

While Raonic mustered a win against Federer in the Paris Masters, victory over Djokovic or Rafael Nadal remained elusive.

Dimitrov's impressive defeat of Murray at Wimbledon was followed by a thrilling encounter with Djokovic, who took the final two sets in tiebreaks. The Bulgarian also failed to win against the top 3.

Nishikori, under the tutelage of Michael Chang, may yet be an even better bet to break the stranglehold. His punishing forehand and two-handed backhand drew the admiration of many in 2014.

The influence of Stefan Edberg and Boris Becker in the games of Federer and Djokovic has been evident, but both players were already on their way to becoming greats.

If Chang's good work continues, then Nishikori's trip to the finals of the U.S. Open last season will be the first of many. 

Will Eugenie Bouchard Better 2014?

Elise Amendola/Associated Press

A sobering WTA Finals will have given Eugenie Bouchard enough to pick over during the offseason.

The three defeats didn't taint the year but provided a realistic marker of where the Canadian is at.

A similarly grounding result against Petra Kvitova at Wimbledon shouldn't colour the achievement of reaching a Grand Slam final at just 19 years old.

To develop the necessary parts of her game in such a short space of time will make it difficult for Bouchard to better 2014.

Two other Grand Slam semi-finals, at the Australian Open and French Open, may encourage a loss of perspective from those outside the game should Bouchard not recapture 2014's brilliance immediately.

The departure of coach Nick Saviano should also be accounted for, and the forthcoming 12 months promise to draw even more intense scrutiny. 

Bouchard's fighting instinct will need to be stronger than ever. The spirit that led Simon Briggs of The Telegraph to call her "Tarzan and Jane rolled into one" must come to the fore.

Which of the Women's Young Stars Will Truly Emerge in 2015?

Elise Amendola/Associated Press

A surge of talented young players, hungry from successful seasons, will give the women's game a timely boost.

Serena Williams, on the other hand, will arrive in 2015 off the back of her 18th Grand Slam and the WTA Finals title.

Maria Sharapova, Kvitova and the retired Li Na won the other major tournaments, but the ability from lower down the rankings was palpable and will inspire confidence.

Garcia enjoyed victories over Venus Williams and Agnieszka Radwanska on her way to the Wuhan quarter-finals. The 21-year-old also knocked out Angelique Kerber and Sara Errani in Madrid.

Bencic made the quarter-finals at the U.S. Open, beating Kerber and Jelena Jankovic along the way.

Matthew Ponsford wrote for CNN that the 17-year-old is regarded as "the new [Martina] Hingis". A number of impressive performances this year have supported that (if not corroborated it).

There is also Muguruza, the 21-year-old responsible for knocking Williams out of the French Open. Wins against Caroline Wozniacki and Simona Halep this year also lend substance to the idea that Muguruza could be one to watch.

Andy Murray's Coaching Shake-Up

Tim Ireland/Associated Press

As much as Murray might have preferred to have avoided an early 2015 subplot, events over the last week have made that an impossibility.

The Scot parted with coaching pair Vallverdu and Green. That it will also be his first full season since Ivan Lendl's departure makes the plot even more intriguing. 

Vallverdu has been a long-time confidant of Murray's, a constant throughout his attempts to win a Grand Slam, conquer Wimbledon and claim Olympic gold.

Lendl's unmoved, steely presence was replaced by the more open Amelie Mauresmo. 

Sky Sports' Barry Cowan believes that Murray was never likely to part with Mauresmo, having only appointed her in the middle of the year, as "it's almost admitting that it hasn't quite worked."

The two-time Grand Slam winner perhaps didn't earn the praise she should have for her role in Murray's outstanding crusade to make the ATP World Tour Finals.

But Murray's faith in her is unmoved. That, it seems, is the only thing to have remained the same in a period of upheaval.

Which Young Player Will Break Through?

Sang Tan/Associated Press

Nick Kyrgios stunned Nadal at Wimbledon in July and played the crowd into submission with some remarkable shots. The Australian is a certainty to build on that outstanding performance in 2015.

John McEnroe is among those to have backed the 19-year-old for greatness, telling The Daily Telegraph, "When I saw him at Wimbledon, when he made his breakthrough, I thought this guy is going to be top five in the world for sure."

David Goffin has, arguably, already broken through following a successful second half of the season in which he won six tournaments in just under three months.

Despite four of those wins coming in Challenger events, the Belgian has established a winning rhythm in his game that shouldn't be underestimated heading into the new season.

Dominic Thiem is another young player to have excelled on the big stage this year, having beaten Ernests Gulbis and Feliciano Lopez at the U.S. Open.

The Austrian, ranked No. 39, is hardly an unknown quantity but perhaps still has an element of surprise that could carry him to the latter stages of tournaments.