David Vidal had a strong 2011 season with the Dayton Dragons and carried that success over to Bakersfield in 2012 before having some struggles after a quick promotion to Double-A Pensacola. Over the last two seasons there have been some swing mechanic changes made. The two videos that I looked at here were from April of 2011 with Dayton and from August of 2012 with Pensacola.
Here in the first frame, pre-swing we can see a few different things going on.
Two things jump out immediately here. First is the position of the elbow. On the left, in 2011, Vidal had a bit of a flap that he did with his elbow. That in turn caused his hands to also be set up a little bit lower in his pre-swing set up (this was eliminated at some point during the 2011 season while with Dayton). As he began his swing, his elbow got into a matching position to the 2012 position, though his hands were slightly lower than they were in 2012.
In this comparison we see the big changes made in what Vidal did with his...