Baseball Prospectus released their pitch tunnels stats last offseason, opening up a new way to analyze pitchers. The basic concept of the several statistics is centered around letting go of the baseball at the same location consistently.
Kyle Hendricks’ sinker/changeup sequence ranks #1 in release:tunnel ratio. Baseball Prospectus defines release:tunnel as “the ratio of a pitcher’s release differential to their tunnel differential.” Specifically, “pitchers with smaller Release:Tunnel Ratios have smaller differentiation between pitches through the tunnel point, making it more difficult for opposing hitters to distinguish them in theory.”
Jake Arrieta also has significantly improved his release point tunnels, which can be read here.