The last 15 years of the ATP Tour have produced countless memorable tennis betting moments and created numerous headlines around the world.
The game has been dominated by the so-called "Big Four" which comprises of Roger Federer, Rafa Nadal, Novak Djokovic and Andy Murray.
Many challengers have threatened to break the dominance of this all-conquering quartet but they've been unable to dethrone this fantastic foursome.
However, after years of being at the top of their game, tennis betting punters and fans are now wondering if we're finally witnessing the changing of the guard.
Injuries, inconsistency and the ageing process have slowly begun to take their toll on these iconic athletes and 2019 could be the year that tennis begins to usher in a new generation of future stars.
The Big Four
At least two of these four players have occupied the top two spots in the rankings continuously since July 2005 and between them, they've amassed an unprecedented 295 titles.
They've won 50 of the last 55 men's grand slam titles and all four of them have reached number one at some stage during this period.
Roger Federer
The Swiss maestro was the first of the "big four" to break through and the 37-year old has a dedicated fanbase who have enjoyed watching him dominate the game over the past decade.
Boasting a career record of 1180-260 and clocking up 199 career titles, he's enjoyed the most success of the quartet and is still going strong despite his advancing years.
He's dropped several hints about the possibility of retiring but he still reached the semi-finals at the O2 in November 2018 and looks set to continue playing at the highest level for at least another season.
Federer has enjoyed terrific success at the Australian Open in recent years. He's been priced up as the third favourite at 6/1 for the first Grand Slam of the season and will be returning to Melbourne to defend his title.
Rafael Nadal
The "King of Clay" has been arguably less consistent throughout his career owing to a number of injury setbacks but if the affable Mallorcan manages to keep himself fit, he is a joy to watch.
He thrives at certain tournaments, with the 11-time French Open winner enjoying success in Paris, Rome, Cincinnati and Monte Carlo.
He is one of the youngest Grand Slam winners in the history of the game, bursting onto the scene at the age of 19 and securing his first French Open title in 2005.
Novak Djokovic
The Serbian has 14 major titles to his name and is admired for his consistency. He is able to perform on all surfaces and his accuracy and ruthlessness have helped him become one of the sport's most decorated competitors.
He broke into the top 100 for the first time in 2005 and was the first player to break the duopoly of Federer and Nadal.
He's ended the year as the number one ranked player on five different occasions and despite some injury lay-offs in 2018, he still managed to end the year strongly.
He's 13/10 for the 2019 Australian Open and has won in Melbourne on five occasions since 2013.
Andy Murray
There are some fans who object to the inclusion of Andy Murray in the "big four" but the Scot has enjoyed enormous success over the past decade and has spent plenty of time at the top of the rankings.
He may not have won the French or Australian Open but his success at Wimbledon, in the US Open and at the Olympics should not be overlooked.
Murray is the only one of the quartet not to have completed a career Grand Slam but does have 45 career titles to his name and remains the only tennis player in the history of the game to have secured two Olympic single titles.
How Will They Fare In 2019?
At the age of 31, Andy Murray still has plenty of time to recapture the form that saw him top the ATP rankings but he must overcome a long injury lay-off and that won't be easy.
He played just 12 matches in 2018 and getting up to speed in time for the Australian Open will be far from straightforward. He's 14/1 in the 2019 Wimbledon betting and he may have to set his sights on a successful grass court campaign instead.
Murray's injury record may just see him feature sporadically throughout the year and he is susceptible to younger, fitter players, who may just have the edge on the Scot.
2019 could be Roger Federer's swansong and he'll be 38-years old at the US Open.
He still managed to win 46 times during the 2018 season and the Swiss star is likely to retire before the going gets tough. Federer may shortly choose to hand the baton over to the next generation.
Rafa Nadal hasn't played since the US Open and missed the ATP Finals through injury. He still enjoyed a great season, however, being defeated on just four occasions.
He's got to manage his body carefully over the next twelve months and there's no guarantee he will feature during the early part of the season.
It's been a long time since Novak Djokovic lost ten times in a calendar year but 2018 was a struggle for the Serbian and we may see his influence fade over the next twelve months.
Djokovic still has the class to win smaller tournaments but his ability to succeed in Grand Slams may be a thing of the past.
Who Are The Next Generation?
Alexander Zverev
Zverev is the highest ranked player outside of the "Big Four" and was triumphant at the ATP Tour Finals in November.
He won 47 times in 2018 and although there are still question marks about his consistency, he showed his ability to manage the occasion when beating both Roger Federer and Novak Djokovic at the O2.
The German is just 20-years old and appears to have a bright future ahead of him and may be the next player to reach number one in the rankings.
Dominic Thiem
It may feel like the Austrian has been around forever but, at just 25-years-old, his best years are surely ahead of him.
His lack of nous on grass courts may count against him in the long run but he will certainly give any player a run for his money and is likely to be lurking around the top five for many years to come.
Stefanos Tsipitas
After losing ten of his 14 tour matches last season, 2018 has been a breakout year for the Greek and there should be plenty more to come.
He beat Novak Djokovic at the Canadian Masters and also saw off the aforementioned duo of Alexander Zverev and Dominic Thiem. He's the youngest of the trio and should be able to make a name for himself in 2019.
Gradual Shift In Dynamics?
The changing of the guard isn't likely to happen overnight but 2019 looks set to be a significant year for the sport.
Tennis fans have become accustomed to the success of the all-conquering foursome but their influence is starting to wane and younger players are beginning to take their place.
Staying at the top of your game is far from straightforward and Roger Federer, Novak Djokovic, Rafa Nadal and Andy Murray should all be commended for remaining incredibly consistent throughout their respective careers.
However, they can't stick around forever and the next generation of players are slowly starting to chip away at the quartet and it is a very exciting time to be a tennis fan.
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