Hi
I dont think a treadmill provides even 50% of the benefit that you would get from the same time training outside. You can t recreate the immediate dynamic movements required for effective football running training on a treadmill.
If you consider the kind of movements and automatic shifts in speed that will be required in a game...ie...walking or jogging to a full on sprint in a split second, this is the kind of explosive power and speed he needs to work on.
besides interval training which an decent footie team will provide at training, exercises that will help are things like
jump squats. These will help strengthen and increase the explosive power of the major leg muscles. See the link below
http://www.shapefit.com/quadriceps-exercises-freehand-jump-squats.html
In my humble opinion they should be done as follows.
* start in a fully erect position as shown with arms crossed in front.
* slowly lower down until the crease of the hip is inline with the joint of the knee. At this point the bum should be sticking out, chest should be inflated and shoulderblades high....an ideal position to accelerate upward with maximum force. take about 3 second to lower. nice and slow.
* from the bottom, keep the chin up and drive through the heels, not the toes as hard as you can which should see you jump. hands can be removed from the crossed position to balance.
SJ