Culture shock sets in for a hitter when they begin to face faster pitching. The thought of not being able to catch up to the heat causes them to press, which leads to bad habits such as lunging, squeezing the bat tight, and moving their head around like a dolphin out of water. It's not an easy transition for a hitter, but with lots of reps, it is very doable. The key here has to do with the timing of their load, and their bat path.
THE LOAD: When facing slow to medium paced pitching, a hitter can get away with loading their hands and hips while the pitch is flying in their direction. Against faster pitching, the hitter needs to get his hands and hips prepared prior to the release of the ball from the pitcher's hand. This will give them some much needed 'extra time' to recognize the pitch, before going at it.
THE BAT PATH: Secondly, from the loaded position, the hitter must take their hands forward. This seems to be foreign for most, as hitters are born with this innate urge to make a long swing.
A “Big Swing" is not a good swing.
Once the pitch is released, the barrel of the bat can't go backwards or down. I call those areas "burger land," and we don't have time to go get a burger. The barrel has to quickly get out in front of the hitters’ body if they wish to hit the ball hard.
The most consistent hitters usually have the simplest swings. They sacrifice the big stride for a simple coil and uncoil of the hips. Take Daniel Murphy and Kris Bryant for instance. Their swing is very "A to B", quiet yet quick. They use their core muscles, instead of their flimsy arms and feet. They were the best two hitters in the National League last year, AND they had power.
I know from experience, turning a long swing into a quick swing is no walk in the park. It takes lots of work in the cage. But as a wise man once said, "Champions are made in the batting cage."