It means that if you lift chest/shoulder/triceps mondays, lift it again on friday meaning tuesday is back/biceps and wednesday is legs. I would take a day off after lifting legs as it takes a lot of energy out of your body. You could even take 2 days off, but since you won't be lifting a really heavy weight (10+ reps a set), you will recover faster. Shouldn't be more than 3 day cycle. Training muscle groups that work together. Chest one day, back then next, and then legs. That's all you need. take a day or even 2 days off if you are really exhausted, and go again. If you have a leg lifting day that falls on agility training, do your agility training first. Lifting first will cause injury due to tight muscles.
Oh, and don't do skull crusher. Bad for a throwing arm in the elbow. stick to dips and tricep ropes.
On back days, do cable rows, dumb bell lat pulldowns or pullups. I prefer pullups, but I do both of them to keep things fresh. Reverse flies are really good for your decellerators like the rear delt and are a good excercise to do. Do not do dead lifts. Feilding ground balls while recovering from doing deadlifts is asking for injury in the back or the hamstring.
One thing I did back in HS that I really like was I would get the tricep rope and put on a decent weight and go threw the swinging motion from both sides. It will help power and getting the head of the bat out quicker in the zone. It's an idea.