In terms of general prep for preseason you just need to be doing simple things like stretching, squats, sit ups and press-ups, a mile and a half is all you need if you are running, 2miles if you are jogging. plenty of fluids before and after at key times. people working on strength programmes need to keep them light until you can marry them into your baseball routines as this could distort muscle memory and fluidity of motion.
With the bat: 50 dry swings with increasing application and focus on an imaginary pitch coming in at varying positions and speeds.
60-70 ball-less throws to an imaginary target, full body-rock, back and forward on the release. Reach and collect,repeat.
Dip and lower to motion a groundball pick-up every 6-7 throws.
If you feel you would like a guide to supplement your running, this is a moderate schedule to incorporate.
Stretch, legs, back, arms,neck and your other preferences.
3 sets of 15 press-ups; 3 set 15 sit-ups, 20 flat squats, 10 on your toes squats, 10 star jumps, 15 squat thrusts. increase up to double the number as you need or progress.
If you find these sequences little boring, use a circuit of sets of 5 in a ongoing sequence. ie 5 sits, 5 press, 5 squats, 5 stars, 5 thrusts---etc. don't forget to take an appropriate drink at regular intervals.
Remember: Increasing sleep volume by 45mins per night gives 5 plus hours of extra rest per week. With your weekend lie-in, you can steal an extra valuable nights rest per week. Thats 14% extra sleep.