"Inside Baseball" by Tom Verducci - SI.com

Ever wonder why some pitchers have "hop" on their fastball and others don't? Why two pitchers who both ostensibly throw 94-mph heaters can perform so differently on the mound? Well a Danish company is using modern technology to compile a host of new data on pitchers' strengths. And it may make the radar gun obsolete.

http://sportsillustrated.cnn.com/2011/writers/tom_verducci/04/12/fastballs.trackman/index.html?eref=sihp