..............

For his changeup, Felix uses a grip that we haven't seen other pitchers use.  He seems to keep his index finger on the ball more, as opposed to making an "OK" sign with it.  He places his middle and ring finger actually on the seams, and he seems to otherwise throw it just like a fastball.

So when Tom Wilhelmsen asked Felix to teach it to him, Felix said "I dunno man, I just throw it."  Wilhelmsen probably figured that Felix was guarding secrets.  My own guess would be that Felix actually does just throw it - that there's nothing much to explain.  It just so happens that that grip, with Felix' particular hand shape, works a serendipitous little miracle.

Check out this velocity graph for Felix:

 ..............

The orange line is the changeup, and the green line is the fastball.  See how they are converging over the years?  You can see it even better on this page.  And now, in 2012, they have finally converged completely:  F/X classifies all of Felix' fastballs and changeups as one pitch!

The takeaway point here is that Felix' changeup is a miracle pitch.  Here, let's look at two more charts:

 ...................

his fastball.

In any case, all systems 100% A-OK for the miracle Felix changeup...