Zones 1, 2, and 3 are collectively called the Go Zone.  They are green to represent passage and should be the first Zones you get comfortable throwing in.  Pitches that hit the Go Zone are quality strikes no matter what pitch you throw. The 2 Zone is not as tall because it is easier to hit a pitch high in the strike-zone over the middle of the plate compared to a pitch in the 1 or 3 Zone (the inner or outer-thirds of the plate). Every pitcher wants to stay away from the belt-high pitch in the middle of the plate. 

To command pitches in the Go Zone, you must have a downhill plane on the flight of the baseball to reach the bottom two-thirds of the strike-zone.  When a pitch is thrown on a downhill plane the hitter is more likely to hit the top of the ball, producing a ground ball or a swing and miss.  Its more difficult for the hitter to recognize the velocity of the pitch and the pitch type when pitches are in or below the Go Zone. 

If the pitch is flat, or ends up above the Go Zone and below the letters, it is much easier for the hitter to square the ball at contact.  The objective of the hitter is to put the bat on the plane of the ball for as long as possible. When a flat pitch, or a pitch with horizontal movement, crosses the plate, it stays in the hitters bat path longer than a pitch with a downhill plane.

Flat planed pitches move horizontally early in ball flight compared to the short late movement of pitches with a downhill plane.  The earlier the ball moves out of the pitchers hand the more time the hitter has to recognize and time the pitch.  

Use the Go Zones to get ahead of the hitter in 0-0 counts, getting ahead puts the hitter in a defensive mode and makes them protect the plate.  Getting ahead in the count also gives you more pitch-choices a hitter is willing to swing at. As you get ahead in the count, pitch type, pitch Lokation, and sequence possibilities increase for the hitter. If you are unable to command the Go Zone in 0-0 counts and hitters get ahead in the count, the odds of them seeing a fastball go up.  

The further behind in the count a hitter falls (0-1, 0-2, 1-2), the more likely they will expand their strike-zone.  This means they will swing at a higher percentage of pitches toward the edges of the plate or under the strike-zone (4, 5, 6 Chase Zones).  It gives the hitter a sense of urgency.  They are more likely to protect the plate and expand the strike-zone while behind. Statistically this will reduce the hitter’s batting average and power numbers.

Getting ahead in the count 0-1 puts you on the offensive and gives you more control of the at-bat. Getting ahead puts the hitter is in a defensive mode and you have more options of pitches and Lokations the hitter will swing at. While behind, they must protect the plate and defend against more pitch possibilities.

If the hitter is behind in the count with two strikes they must protect the entire plate including the corners. That adds up to nearly 24 inches of space to defend. And if they must also consider two or three possible pitches in multiple Lokations, they're timing will generally be at its worst. This is why hitters are taught to shorten their swings with two strikes, so they have longer to recognize a pitch before putting a swing on it.

If you consistently get behind in the count, 1-0, 2-0, 3-0, 2-1 or 3-1, which are called hitter's counts, you must throw strikes to avoid a walk. When the batter is in a hitter's count, they can be very selective and look for the perfect pitch because they understand you have to throw a strike to avoid a walk. This narrows pitch Lokations and possibilities a hitter has to take into consideration and makes timing easier. 

When you are forced to throw a strike, the percentage of fastballs usually increases. When a hitter expects a fastball and gets a fastball, their timing is at its best.  This is when the fastball actually looks slower to the hitter than it actually is because timing is good.  We call this decreasing perceived velocity. 

When a hitter is ahead in the count they can look for one pitch in one area. This limits the areas they have to protect against and the number of pitches they are willing to swing at.  In a 2-0, 2-1, 3-0 or 3-1 count, a hitter can cut the plate into sections and decide beforehand which pitches he is willing to swing at. A fastball is the most common pitch a hitter will decide to “sit on” or expect.  Most professional hitters use this approach to some extent.