Top 5 contenders for No. 1 ranking in Men's Tennis in 2018

#4 Grigor Dimitrov

Dimitrov has been long touted as the successor to Federer

Grigor Dimitrov finished the 2017 season on a high by winning the Nitto ATP Finals. It was only the third time since 2003 that a player outside the Big Four won the prestigious tournament, which only the top 8 qualify to play.

He has had a decent start to his 2018 campaign, making it to the quarterfinals of the Australian Open. He had a great run at Rotterdam, finishing as a runner-up to Roger Federer. Dimitrov reached the finals at Rotterdam without dropping a set.

Although he was quite inconsistent in the previous tournaments at Miami and Indian Wells, the upcoming clay-court season provides him with ample opportunity to gain valuable points and boost up his ranking.

Federer has already announced his absence from the clay-court swing and Djokovic, Murray and Wawrinka are clearly struggling with form and fitness issues. With Nadal also making a comeback from injury, this might be Dimitrov's best chance to dominate the next few months on tour if he can improve his consistency.

Dimitrov also has a good chance at Grand Slams and rest of the Masters 1000 tournaments this year as he isn't defending a lot of points, with a title run at Cincinnati last year being the only result of major significance.

He is defending only 775 points in the remaining Grand Slams and Masters excluding Cincinnati. With form on his side and an improved ranking compared to last year, Dimitrov can prove to be a major threat to the old guard.

Year-end no. 1 ranking might still be a distant dream for the current world no. 4, but if he can produce the level of tennis that he is usually expected to, anything is possible.