Teach keepers not to dive on penalty kicks.

Goal Keepers in general are an odd breed. Deciding to be a goalie in the first place doesn't make much sense to me, regardless, keepers are vital to the game and the overall success of any team. For the longest time, however, I just can't seem to figure out the logic behind why keepers dive to the side on a penalty kick. Obviously they are guessing or making an attempt at picking a side the penalty taker might go, but is this really the best effort in minimizing the statistically advantage the shooter has or in maximizing the keepers chances of making a save?

First off, as a former player and current coach I was taught and currently teach players to try and stay on their feet as much as possible. You can't change direction if you are laying on the ground or you're off your feet in the air. This applies to keepers too. If a keeper decides to dive for a ball and the ball is struck down the center, there is no chance for the save even if the ball might be inches away from the keepers feet.

Usually the keeper starts out on the line in the center of the goal. If the keeper were to decide not to move, generally, the green areas are where most likely the keeper will not make a save. The red zone, the keeper has a reasonable chance of making a save depending on the reaction ability of the keeper and pace of the shot. Statistically, the keeper has a little less then 50% chance of making a save based on the area of the goal being covered.

Realistically, the chances are not equal to a little less than 50% because most penalty shots are placed in the green zones of the goal. So based on this logic, the keeper should pick a side to attempt to stop the shot.

If, let's say, the keeper chooses to dive to his/her right, its not just picking a side, the keeper must also choose to dive low, mid range or high. Either way, statistically speaking, the keepers chances are instantaneously reduced to around a quarter percent of a chance of making a save. At the professional level, most penalties are placed in the corner low to the ground so if a keeper were to choose to dive, dive to the middle and low to the ground.

What if the keeper picks a side and simply decides to cover that half of the goal? Statistically speaking, there is a much better chance for the keeper to make a decent attempt at the shot.

Yes but wouldn't the shooter just read the keepers movement? 

Some do but most penalty shooters don't. Out of 10 penalty takers, I think it would be fair to geustimate there would be 1 maybe 2 that would actually analyze the the keepers movement to decide which way to go on the strike. Penalty takers are neverous enough and the vast majority are coached to pick a side, focus on the ball and if it's well placed and hit with enough pace, the ball should hit the back of the net. Especially if the goalie dives covering only around a quarter percent of the goal. If every keeper were to adopt this non-diving methode of penalty stopping, penalty takers might change their methodes, but this change and forcing the kicker to look at the keeper is an advantage to the keeper. Mind tricks and deception can now be implemented aiding the keeper in raising of preventing a goal. 

Would the keeper get in a set position in time? Even if the keeper was not able to get all the way across and leaves some space near the post for the ball to go, the chances of the shooter placing the ball right inside the post are also small. This could actually be part of the strategy in case the keeper believes there might be a shot down the center of the goal. 

Clearly, the timing of the keepers movement is important. Too soon, the shooter might have the time to change their decision. Too late, the keeper might not get across to cover as much of the goal to make a save. Right when the shooter puts his/her head down to focus on the ball and strike it, would be the right time to quickly shuffle over 2 steps.

Although, I think this method is worth considering at all levels of the game, there can be significant greater successful at the youth levels or even the lower college, amateur or semi-pro levels where the accuracy and pace of the shot might not justify making a desperate dive to the corner. The reason is because the shooter might miss hit the ball and it most likely won't be placed perfectly on the in side netting of the goal.

Let's analyze a real life example, the Champions League Final 2008 Penalty Shootout between Manchester United and Chelsea. Watch the footage and decide for yourself:

http://www.youtube.com/watch?v=vKanEXkBRZw