When you run sprint, your knee lifts up and over then comes down to the ground which is where the magic happens.
Your ability to hit the ground on each and every contact in a forceful and powerful manner is the foundation of how you'll sprint, run or jog.
Elite sprinters train to perfect and each and every sequence in a 100m sprint in ridiculous detail because .1-2.secs can be the difference between a gold medal and a no place result.
They execute knee lift, foot/ankle stiffness, core stiffness, force transfer and a million other things but what they started with to be fast in the first place is the natural ability to develop great force upon ground contact.
When you hit the ground in a single leg stance, you can be putting 5 - 6 x your own bodyweight through that single leg every single step.
Your foot needs to be able to hit the ground and with limited deformity, absorb all that external force from each step and redistribute it back into the ground.
This all needs to be performed in as little .15 of a second.
FYI, running is about .2 of a sec, jogging is about .25of a sec and fast walking is about .6 of a sec.
As you can see, there's not a lot of time to get things done during walking, let alone at top speed.
If you can't develop this kind of force naturally, and if you're not very fast right now then you aren't (like most of us), then you can train to do this.
All this involves is a to GET STRONGER.
Yep, that's it.
You simply need to get stronger at either a deadlift or squat movement.
If you've not done much weights work before, especially for the upper body, then this can increase quite dramatically if you follow a program designed specifically for it.
If you're not really into weights then don't sweat, I'm not against you simply working just 1 exercise and nothing else because this is all about improving performance so we can ultra specific no problems.
Local/amateur footy clubs would be extremely wise to set aside as little as $300 - 400 to purchase some weight plates and a bar of some description and set it up at the footy club.
Set aside 10 - 15mins pre and/or post training for your players to hit the exercise of choice for 3 - 5 sets where 2/week would be almost perfect here.
Actually make it part of team training and like everything else, track every players numbers so that improvement can be seen over time.
You don't need a mammoth 5 day training program for this, nor should you be using one for footy anyway.
Just 1 exercise (my choice for practicality reasons is the Trap Bar Deadlift), 3 - 5 sets x 8 - 3 reps, 2 - 3mins rest between sets, all reps performed explosively.
In the end you'll be able to use more of the force you absorb from each step that like a pumped up footy, will bounce faster and further upon each step so you'll cover more ground per step = increased speed.