Raonic
The Good - has steadily improved throughout his career. Can dominate with his serve (one of the three best in tennis). Has developed into one of the more consistent players on tour.
The Bad - return game is too weak to challenge elite opponents. Movement limits his potential. I think his upside is the lowest of the four.
Nishikori
The Good - the best mover of the group. Defends well and is solid off both wings. Sneaky/underrated power. Has found a new level of consistency that was lacking previously.
The Bad - could use more variety. Can become too defensive. Power may be underrated, but is it enough to win majors, especially if he's going to operate solely from the baseline. Injury concerns.
Dimitrov
The Good - higher upside than Raonic and Nishikori. He moves well enough to defend at an elite level and his combination of power, variety and all-court skills gives him the potential to be an effective offensive player. Had made noticeable improvements every year through 2014.
The Bad - has never put his vast array of skills together into a consistent, repeatable strategy/style. Can get glued to the baseline and become too defensive. Off to a disappointing start in 2015. Needs to settle on a racquet.
Kyrgios
The Good - arguably the highest upside of the 4. Possesses the best combination of power and movement. Serve and forehand are both huge weapons. Can do serious damage with backhand as well. Seems to thrive and raise his level on the biggest stage.
The Bad - inexperience. Needs to improve consistency/reliability of groundstrokes, especially the backhand.
I'm inclined to go with Kyrgios. If you asked me which guy I'm most confident in to win a major before his career is over, I'd say Kyrgios without a doubt. That doesn't mean I don't think the others can't, but I'd be less surprised if any of them finished major-less. So, for that reason, I have to go with the young Aussie.
