ATP World Tour tennis finalists
Tomas Berdych (R) takes a 'selfie' with fellow tennis players (L to R) Roger Federer, Stan Wawrinka, Novak Djokovic, Kei Nishikori, Andy Murray, Milos Raonic and Marin Cilic at the O2 Arena in London November 7, 2014. The men's ATP World Tour tennis finals take place at the O2 Arena from Sunday for a week Reuters

As the best player in tennis, Novak Djokovic knows that other guys will be gunning for his spot as world No. 1 in 2015. Aside from the usual challenges from the regular top contenders like Roger Federer and Rafael Nadal, the Serbian believes that other young guys will be on the rise soon mentioning the likes of Kei Nishikori, Milos Raonic and Grigor Dimitrov as the players to watch next season.

Djokovic is currently rated the top player in tennis but has only won one Grand Slam title in the 2014 season, when four different players won the four majors tournaments. Stanisla Wawrinka (Switzerland) won the Australian Open, Nadal took another French Open title; Djokovic ruled the Wimbledon Championship and Marin Cilc was victorious in the final slam of the year, US Open.

"Obviously, [Marin] Cilic, [Stanislas] Wawrinka and some new names who have been winning grand-slam titles and challenging the best and winning against the best in the big events - they have proven to everybody that it is possible,” Djokovic said in a press conference for the International Premiere Tennis League. “The dominance of first of all Roger and Rafa over the years was fantastic. Then Andy Murray and myself, we got into the mix and us four have been winning most of the big events in the last six, seven, eight years.”

"Now it's normal to expect that there is a new generation of players, younger players that are right at the top like Nishikori, [Milos] Raonic [and Grigor] Dimitrov, who have the quality to win against the best and they have done that. It's definitely going to be an interesting year.”

Among the three names mentioned, Nishikori from Japan has had the most impressive campaign in the 2014 season. Nishikori rose to No. 5 in the ATP Rankings by end of year— his career-high. The 24-year-old Japanese also qualified for the World Tour Finals becoming the first Asian to make that season finale tournament.

Meanwhile Dimitrov and Raonic, both at 23 years old, have also reached career-highs in their respective ATP Rankings at some point during the 2014 season; Dimitrov reached No. 8 in August and Raonic went as high as No. 6 in July.

Djokovic remains the top favourite in any tournament entering the 2015 season but with injuries to Nadal and the age factor for Federer, the Serbian might just be right in saying that 2015 will be the year that the young guns start becoming legit contenders for tennis' top spots.