The ATP Tour never fails to surprise year after year.
The story lines littered throughout the tour from the top-10 to the Challenger Tour are what make for such fixating viewing all year long, and going into 2016, things are no different.
Here are 11 different players, each representing their 10th of the top 100 (100-91, 90-81, etc) that the keen ATP viewer should keep an eye on for this year.
Honourable (outside top 100) mention: Juan Martin del Potro
Super-talented Argentine Juan Martin del Potro has battled a wrist injury for most of his career, and in 2015, for the second straight year, he was forced into season-ending surgery.
Currently ranked 590, his last tournament was the Miami Masters in March last year. The tennis hopes of a nation lie on whether del Potro can reach his incredible top form we saw over five years ago when he won the US Open.
#96 – Taro Daniel (Japan)
Taro Daniel is another young talented Japanese player slowly making his way up the rankings.
Daniel, 22, is the Japanese number four, and recorded a career best year last year, winning three Challenger titles and notching his first Davis Cup win.
#83 – Alexander Zverev (Germany)
18 year-old Alexander Zverev is a former junior world No.1.
Slowly rising the rankings, the teenager won in his first ever Grand Slam match last year, defeating Teymuraz Gabasvhili in a five-set thriller at Wimbledon.
#80 – Thanasi Kokkinakis (Australia)
Just one of Australia's swag of young tennis talent, Thanasi Kokkinakis showed last year why some rate him higher than fellow countryman Nick Kyrgios.
Kokkinakis' big hitting and athletic 6'5” frame is built in the model of the modern tennis player. He will hope to be top-50 and beyond by the end of the year.
#69 – Dennis Kudla (United States of America)
Kudla made headlines last year when he was the last American standing at Wimbledon – narrowly beaten in the fourth round by Marin Cilic.
Still only 23, Kudla has plenty of tennis left in him. It's taken him a few years to put things together, but he finally looks to be heading in the right direction.
#51 – Hyeon Chung (South Korea)
If he were just one rank higher, Hyeon Chung would be the second-youngest man in the top 50.
The young South Korean was earmarked as a great talent, but was not expected to rise this quickly. His seeking out of the help of former world No.2 Michael Chang shows the kind of wisdom of the next Asian tennis superstar.
#44 – Borna Coric (Croatia)
The Croatian, who only just turned 19, is not physically imposing (6'1”, 75kgs), but is pound-for-pound just about the most talented player on tour. He has the game to match it with the big guns and is a star in the making.
#33 – Joao Sousa (Portugal)
Joao Sousa was a quiet achiever last year – a victory in Valencia and career high ranking of #33 is a pretty good year by the standards of most.
No-one is expecting Sousa to take on the top-10, or win and Grand Slams, but with the year he had last year, one expected him to be a constant ATP 250 and 500 presence.
#30 – Nick Kyrgios (Australia)
The second of Australia's young stars, Nick Kyrgios divided tennis viewers all year last year with his antics both on and off the court.
However, one thing is undeniable – if Kyrgios gets his head straight, he is a future Grand Slam champion.
#19 – Benoit Paire (France)
With a flair for the dramatic, Benoit Paire has been around the block in the top 100 in his short career, but finally looks to be where his talent demands.
The big question for Paire is, how high can his star rise? Can he put together his talent and come up with a game that can win the big ones?
#5 – Rafael Nadal (Spain)
Any top-10 player could've been named as one to watch for this year, but former world No.1 Rafael Nadal might just prove the doubters wrong this year and push for another Grand Slam title.
It's almost impossible to believe that Rafael Nadal is on the younger side of the top-10 – but if he manages to get himself healthy, he is still well within reach of a Grand Slam.