That's why you begin 12 weeks sooner.
The work you do pre-season will give you an edge in skill, power, and injury prevention. It must also be sport-specific to be effective. This is a 9-12 week period following the off-season Winter Base program and leading to the start of a new season.

Understand the Principles of Power...
A major component of your individual pre-season training should be with baseball equipment (balls and bats). It's the most natural way to ensure your muscles are training through their full range of motion and at the speeds required.

The Pyramid System
This will almost automatically create an opportunity to increase velocity - lighter-weight reps immediately after heavier weights.

Weight training at this time of year isn't for bulk it's for power. Don't measure your progress through weight gain or muscle circumference - you're aiming for muscles that are stronger and quicker from top to bottom.

An aerobic base may need to be maintained by pitchers  to handle the stress of long innings, but everyone else should ease off the endurance training (long runs, step exercises, etc.) to focus on short burst (anaerobic) energy demands.

Batting cages are also safe places to work on your throwing (into the backstop net).

Read before every session in the batting cage or weight room.