1975 the psychologist Csikszentmihalyi pointed out that concentrations is "being totally absorbed in what you do". In his researches he defined this "flow" like this: You know all the time and without thinking what you have to do, you feel extremely demanded, but nevertheless in control, what you do is "flowing" from one step to the next, the concentration comes with one accord, you can lock out everything that could distract you, you even forget time and have no idea for how long it's already going on.
People talking how the experienced the "Flow" all report of the following feelings and characteristics: relaxed, automatic, effortless, plenty of time, confident, positive, clear minded, enjoying, no fear, alert, be master of the situation, mentally focussed, full of drive and energy, loose. Did you experience this already? Were you already so occupied with something, that you did forget about anything else around you? Did you already experience to be taken up with something you enjoyed very much? Observing playing children on can notice they are totally lost in playing, that they only enjoy and never think of any consequences.
A sport in "flow" reaches the maximum concentration.
The question of course is how to get there.
You can't force it to happen, but there are some factors which together with curiosity and the readiness, to try can get you there:
Together with an appropriate mental training (concentration training, self assessment, motivation, finding the right targets) you should be able to get there, to experience it yourself.
And not only in sport- no whatever you do, in school, in your job, during exams and in your daily life.