Borna Coric is the youngest player in the top 50, and he just concluded a solid if not spectacular 2015 season with his loss to Andy Murray in Paris. Coric gained a lot of attention at the end of last year when he got a win over Rafael Nadal, and more attention early this year when he destroyed
Murray in Dubai. But even with these marquee victories, Coric
learned wins simply aren't easy to come by on the ATP Tour no matter how much
promise you have. He ends the season on
a 3 match losing streak and a 25-27 record, but will be in good position to
take a step forward in 2016.
Even though Coric struggled at times, he didn't have that many "bad" losses. Of course he would have liked to have a better record, but how many 18 year olds are going to consistently beat Cilic, Nishikori, Nadal, Anderson, Wawrinka, Tsonga and the other top guys he ran into nearly every week. When he finally took a break from the ATP World Tour to play a Challenger towards the end of the year (like most guys his age are doing) he won it without much trouble. Coric probably figures if everyone has to take their lumps when they first come on tour it's better to do so when you're just 18, and now he'll be able to hit the ground running heading into next season.
Just because Coric has a higher ranking at the moment than his fellow talented teens doesn't necessarily mean he'll end up being the best of the bunch (the pick here is Alexander Zverev). There's lots of examples of talented young players coming up around the same time where whoever peaked first didn't end up having the better career (i.e. Hewitt and Federer). But it's hard to imagine Coric won't at least become a perennial top 15-20 player on tour.
The biggest thing he needs to do is add power to his forehand. The forehand is widely considered the most important shot in today's game, and without a dominant one it's extremely difficult to grab a spot in the top ten. Coric's average forehand tends to sit up with too much spin, and gives his opponents something to attack. If he can turn his forehand into a weapon instead of a slight liability (and it's not crazy to think an 18 year old still has time to add power to that side), Coric could become really scary. Don't be surprised if at this time next year Coric is sitting around 25 in the world.