There's More to Legging out a Triple Than You Might Think

First, let me say that finding the appropriate video clips for this post took forever!  That being said, let's take a closer look at each one because both are very instructive with regards to the responsibilities of the base runner when going for a triple.
This first clip shows a runner legging out a triple in a situation where runners are on 1st and 2nd with one out.  Watch the clip and pay close attention to the part where the camera focuses on the batter going from home plate to third base.  Pay even closer attention to what the runner is looking at as the play unfolds.
Let's now analyze what we just saw.  
As the runner rounds 1st base, he runs with his head up and eyes on the ball so that he can watch the play develop.  As he approaches 2nd base, he quickly glances to see if the 3rd base coach is waving the runner home.  When he sees that the coach is, in fact, sending the preceding runner home, he quickly glances back at the ball and decides whether he can make it to 3rd base.  Go back and look at the clip again if you didn't see it.
In this situation, the 3rd base coach cannot tell him whether to come to 3rd base or not.  He is waving the runner home and cannot wave the batter to 3rd base at the same time.  It is the batter's decision on whether or not to continue to 3rd base.  To make a good decision, the batter must process the following:

• Where the ball is and whether his running speed will beat the ball to 3rd base.  Included in this is knowing the arm strengths of the outfielder and infielders involved.
• The number of outs.  Since there is one out, the runner is more likely to take a chance on getting to 3rd base.  With no outs or two outs, the runner would have been more likely to stop at 2nd base.
• The score and inning.  The batter's team is losing by three runs in the 6th inning before the play.  He knows his hit is driving in two runs and that he becomes the very important tying run.  This is also why he will take the chance with one out to try for 3rd base.  With one out, a runner on 3rd is much easier to score than a runner at 2nd base.

The amazing thing is that he has to process all of this and make the proper decision within the less than 2 second window from the time he rounds 1st base to the time he nears 2nd base.  All the while paying attention to the correct mechanics, lines, and angles of actually running properly.   Of course, he doesn't have the luxury of calling timeout so he can think it over and consult with coaches.  His experience and instincts take over and he just "knows" what to do in the flash of a second.

Here's a second clip that also involves two runners on base in the 6th inning.  The differences are 1) there are two outs instead of one, 2) the runners begin the play on 2nd and 3rd base instead of 1st and 2nd, and 3) the batter's team is down by a lot of runs (8) before the hit.  Watch the clip and see if you notice a difference in how the batter/runner watches the play develop.

You may have noticed that the runner never once looked at the 3rd base coach.  From the moment he hit the ball, his eyes only looked at where the ball was and the bases he needed to touch.  There are two reasons for this.  

1. He doesn't have to worry about the 3rd base coach holding a previous runner at 3rd base.  Starting on 2nd and 3rd, both previous runners will score easily.  
2. On a triple, the batter must decide for himself whether he goes to 3rd base or stays at 2nd base.  He quickly computes all the things listed above from the previous clip and decides for himself whether he can make it based on what he sees.  If he relies on the 3rd base coach to tell him, he will most likely slow down during the process of waiting for the coach to decide.  This slowing down or hesitation before getting to 2nd base can be all it takes for him to be out at 3rd base.  The runner must process all of the information in front of him and decide on his own.

This is contrary to what many young players are taught when it comes to running the bases.  Most are taught to NOT look at the ball while they run so they can run their fastest and hit each base.  They are also taught to follow what the base coaches tell them to do.  Although this is opposite of what major leaguers are expected to do, young players often have not had enough game experience to make all these decisions and execute the mechanics correctly on their own.  However, it's very important that runners be weaned off of this reliance on others when they run.  As they get older, the game will become too fast for this approach to continue to work.
The thinking involved in deciding to go for a triple is at a very high level and all of it must occur within a second or two.  Amazing when you stop to think about it.  But also necessary if you want to play at the higher levels.