By Martyn Herman
LONDON (Reuters) - Borna Coric's profile page on his Facebook account reads simply, "Croatian tennis player on a mission to the top!".
It is a lofty claim but the 17-year-old from Zagreb has already taken giant strides this year, collecting some notable scalps to crack the world's top 100 -- the youngest player to do so since Rafa Nadal burst through in 2003.
Coric's victory over 14-times grand slam champion Nadal in the quarter-finals of the Swiss Indoor tournament last week capped a remarkable 12 months for the latest player to roll off the Croatian production line.
In April he beat former Wimbledon semi-finalist Jerzy Janowicz in five sets in a Davis Cup clash in Poland, in August he qualified for the U.S. Open before beating Lukas Rosol in the first round and a few weeks later he won his first ATP Challenger title in Turkey.
In reaching the semis in Basel his ranking rose to 93, a rise of more than 400 places from last year.
Yet, despite all that, the remarkably self-assured teenager took the bold decision to split with his coach of two years, Briton Ryan Jones, before the Swiss Indoors.
Asked why he had made the decision, Coric spoke with the authority of a player mapping out his destiny.
"It has been a very good two years but we had some small disagreements and when you are traveling for two years with the same guy you can get a bit stuck," Coric told Reuters in an interview.
"I felt it was not as good as before so I thought I shouldn't wait for the bad times to come, I'm gonna find a new coach and I want to do it now.
"If you want to become number one you need to stay on top of everything."
There will be no shortage of applicants for the post but until a new coach is named Coric will continue having daily chats with former Wimbledon champion and Croatian hero Goran Ivanisevic, a man he calls his mentor.
"I talk to Goran every day, he has been a great influence on my career so far," said the teenager. "He's a fighter, like all the Croatian players, and it's great to hear his advice."
Marin Cilic, the player Ivanisevic guided to the U.S. Open title this year, is also a big fan of Coric.
"He's an amazing talent, it's amazing spirit that he has, and he's a big fighter," Cilic told Reuters at the Paris Masters this week.
"He has got something in himself that you can't create, something that God gives you, he doesn't take no for an answer."
Coric had just been crowned U.S. Open junior champion last year when he was called up for Croatia's Davis Cup tie against Britain and a baptism of fire against 2013 Wimbledon winner Andy Murray.
While the 6-3 6-0 6-3 defeat looks an emphatic beating on paper, those who witnessed the 16-year-old in action for the first time were busy scribbling down the name of Coric as a future champion in the making.
"It was a great experience," he said. "In the third set I had a 3-1 lead and a point for 4-1. I think at that moment I realised I could play with these guys and I realised what I needed to do."
Firstly he got stronger, spending two hours a day in the gym to help prepare his 6-foot-1 frame for life on tour.
"It's very physical tennis but I think I have been doing very well on that aspect for the past year now so I have got much stronger and bigger and can cope in a physical way," said Coric.
Apart from 19-year-old Australian Nick Krygios, Coric is the only teenager in the top 100 in the rankings but if proof were needed that he belonged there his 6-2 7-6 defeat of an ailing Nadal provided it.
The Spaniard, who decided to end his season after that defeat because of appendicitis, was not at his best but the Croatian was ruthless against the man he spent seven days training with in Mallorca at the end of last year.
"I was nervous before but at the same time I knew I had to show not too much respect, I needed to be normal," he said.
Coric's style and demeanor, not dissimilar to world number one Novak Djokovic, oozes confidence and he says he wants to reach the top 50 next year.
"I can't stop here, I have to work to achieve something bigger," he said.
"(Having people know who I am) is a good pressure. I know I will have to train harder now, put in more work on the court. But I'm looking forward to next year."
(Additional reporting by Pritha Sarkar, editing by Tony Jimenez)