Nick Bollettieri: My boy Ryan has the fighting attitude to take on Djokovic

You are 20 years old, you have played three matches at Wimbledon, you have never won a senior title and over your young career have lost more single matches than you have won. So here's the question for Ryan Harrison today: how do you beat the best tennis player in the world, the defending champion, a guy who belongs among the greats, a guy who does not possess an obvious weakness?

I spoke to Ryan yesterday and he said, "Nick, I will be ready mentally for this match." You can be assured that – the mentality – is going to be so, so important if he is to challenge Djokovic out there today. This is a battle of the mind.

Here's what I say to my guys: do everything in life with purpose, whether on the sports field or off. Harrison knows this because he has heard me say it at the IMG Bollettieri Academy where he trains and he is someone who has a purpose. I know him well. He comes from a real tennis family. His father, Pat, played at college, his sister is a good player – she will get a scholarship to college – and his younger brother, Christian, 18, has what it takes to follow his big bro into the pro game.

His father deserves a lot of credit for the player Ryan is. So here's the story: off court he is a sensitive nice guy. Get him on that court and he changes: he will go head-to-head, toe-to-toe with anyone, fight tooth and nail. He becomes a guy pumped full of emotion. That is going to be key to his success over the next two to three years, because he can be good if he can get that right,

It's not a question of his playing skills because this boy has all the tools for success. He has a huge forehand, an excellent two-handed backhand, a super slice, a big serve that ranges from 120-130mph and a penetrating second serve, and he is not afraid to come in and volley. He moves and anticipates extremely well – physically he's well built and in good shape.

So far so good, but then look across the net. Holy cow! Novak Djokovic is simply one of the best. Look at his record: No 1 in the world, above players as good as Roger Federer and Rafa Nadal, won four of the last six Slams. The problem is that this guy does not have an outstanding weakness. There isn't one; it's all there, backhand, forehand, serve – effective second serve too. He's got great lower body strength, covers the court like the athlete he is. The volley's there, the drop shot, the slice – and since they sorted his diet out a couple of years ago, his fitness is outstanding, too.

Harrison has a forcing game that means he is not afraid to duel it out with you. He can strike that big forehand – and man, it's huge – from anywhere on the court. That's a weapon he's got to use. He has the guts to say, "If you want to hit a big forehand at me fine, I'll hit it right back at you."

His serve equals his opponents and his stats from his first round win were good – 70 per cent of his first serves were in, at speeds of up to 130mph, which is marginally quicker than Djokovic.

But leave aside all the tennis skills, this will be a mind game. I expect a heck of a match, four sets or more, and it will not be easy for Djokovic. Of course Djokovic is a big favourite, but if Harrison can stay tough up top – not let his mind slip for one minute under the pressure that will come from the Serb – then he can make it tough on the court for Djokovic.