To add on the what P-funk said, I would throw in some injury prevention exercises.
Rotator cuff work, particularly external rotator work, is very beneficial at helping to prevent shoulder injuries and maintain the integrity of their shoulder joint in general. Also, make sure to balance your pressing and pulling movements and use a variety of movement planes to further aid in preventing imbalances.
Work on a variety of planes with the lower body as well. The frontal plane is very important; an example being lateral lunges. This helps to improve hip, knee, and ankle stability as well as improve hip abductor/adductor strength. Movements like this will also transfer well once the players start doing agility work.
I also feel that some level of unbalanced training, whether it be the implement or the surface, is valuable for prehabilitation work. Lately I have been doing squats or push-ups on unstable surfaces to promote stability in my shoulders, ankles, and knees.
Unilateral movements are very important. Don't neglect unilateral squats, lunges, step-ups, etc. This further helps aid in injury prevention by promoting lateral knee stability and such, but as well it is very functional for an athlete to be strong during this type of exercise.