Casper Ruud was the youngest player to directly qualify for the 2021 Nitto ATP Finals. It was a fitting way to cap a breakthrough year.
Former British number 1 Johanna Konta announced her retirement from the sport of tennis on December 1, ending a short but memorable career.
Alex Corretja was a good player in 1998 as he reached the French Open final and won the year-ending ATP Championships.
Boris Becker was one of the best players in the world in the 80s, winning Wimbledon three times in four years.
Emma Raducanu rose to the top of tennis quicker than anyone expected. But staying there will require management - both on and off the court.
Daniil Medvedev, who won the US Open in 2021, is the defending ATP Finals champion having won the title in 2020.
The 20-year-old Jannik Sinner is in with an outside chance of making the ATP Finals. But his 2021 season has been excellent regardless.
The Bryan brothers changed the entire landscape of doubles in Tennis by winning 15 Grand Slams and 1000 matches.
David Nalbandian became the first player to win the year-ending ATP Final title without winning a Grand Slam title.
Diede de Groot and Dylan Alcott achieved the Golden Grand Slam in the same year, redefining dominance in the spor of Tennis.