What is VMI
A player gets familiar with ball movement in his home park
Each team opens spring training in the same environment, which sets their hitting instincts (muscle memory and visual memory) to that climate. At the beginning of a season, it takes approximately three home stands for a team to settle in to its own environment. Once they settle into their home environment, the road trips become more and more confusing, and the visual memory impairment is more pronounced.
VMI stands for Visual Memory Index. It is derived by following each team and each player over a specified number of games, in terms of the location the hitters played within (altitude, air pressure, temperature and humidity; i.e. air density). Visual Memory is formed in a player as he/she is exposed to pitching within similar properties of air that cause the ball to fly through the air on a similar track. An index is calculated which shows when that player has moved to a dissimilar property of air that will necessarily cause the same type of pitch to take a different track to the plate. The greater the index number, the greater the dissimilarity to the team's or player's norm. A non-player might recognize the symptoms of dissimilarity through the following example: Suppose a person has not used a hammer to pound a nail through a board in quite some time. Upon picking up a hammer with, say -- a round hammer head, that person may at first miss, or nearly miss the nail head on the first strike. However, after a few hours of consistent striking a similar nail head, he/she will improve upon the accuracy. This is visual memory and muscle memory working together to create accuracy. This accuracy will continue to improve until either the target (nail head) or the hammer (hammer head) changes enough to create a need for new muscle memory and/or new visual memory.
It is different from traditional thinking only because baseball in general has shifted the thinking from the density of the air to the prowess of the pitcher. The VMI considers the variable air resistance a significant factor in the movement as opposed to blaming and praising the pitcher with no thought to that property which he cannot control.
Our Index is pure
We have left out the issues of talent, who’s pitching, who’s batting, left handed, right handed, on base percentage, slugging percentage, batting average, wins above replacement, era, etc., etc. We know that there are many statistics you can get your hands on, which will help you make decisions of this nature. We, on the other hand want to provide you with something new. We consider ours an index to be added to the standard analysis of players and future performance. Remember VMI - it is catching on with the entire MLB.
VMI is a Visual Memory Index derived from sports weather. As such, it can be used as a Fantasy Baseball Index as well as an index for professional players and managers. We have indexed this visual memory for all big league players in baseball and we have a graph showing how each player reacts to the various degrees of air density exposure.
VMI is not the final analysis
We know that our index does not define the entire game. We also know that statistics in baseball is one of the most difficult from which to see consistency in the player. So our goal is to show a factor, among many, which has a great impact on the game and especially on each player. While using our indexes, don't forget some of the tried and true indicators, such as: the high tendency for a let down after a win; the psychological impact of a team on a roll; and the talent of the pitcher your player must face.
This is primarily a hitter’s index
Pitchers are affected by the climate, as well, but the pitcher’s performance is less affected on a game to game basis, since his decisions are of a wider variety and are more numerous during a game than is an individual hitter's. We track the hitter’s Visual Memory Index so we know when a player will be able to perform at a high level and when he’ll be visually challenged. That is, when his visual memory does not match his muscle memory. When this condition occurs, you will hear through the media that the player will say, "I was just not seeing the ball well today."
The teams in similar environments...
....such as the Midwest during summer months, tend to be more competitive in each others' environment. This is why the central division teams have become known as weaker divisions. When they travel to the east coast or the west coast, the players are taken out of their own hitting environments, because they will now play at sea level and generally it is cooler, so the pitch is moving more.
Domes change the environment, somewhat
When teams play in domes and cool the air in the hottest parts of the summer, they too can become more competitive. Within cooled domes, they have created their own environment and have provided their pitchers with more movement than at some sea level locations. In addition, the hitters in these cooled environments gain the additional advantage of consistently seeing more movement on pitches, so are better prepared to go to certain park venues. However, they have changed only the temperature as relates to the total air density. The barometric pressure cannot be changed except within a pressurized environment and the differences in barometric pressure can be staggering.