Not sure if this has been posted before, but after the discussion on cardio, this has a couple of simple exercises that can be done in a players own time and modified for age group/ability: https://www.fourfourtwo.com/performance/training/three-drills-help-football-endurance Personally, I don't like exercise 2, but 1 and 3 are both very good for sharpness and endurance. They don't require any fancy kit either. If you're not already familiar with 4-4-2 then there's a lot of good articles and resources for football players.