Starters:
Harrison (15-8, 3.30 ERA) vs. Guthrie (3-3, 3.86 ERA)
Guthrie - Change in deception
Supposedly, most of Guthrie's change in performance has come from more deception in his pitching motion according to Dave Eiland. After the jump are 2 videos of him, one from his last start with Colorado and the one from Aug 18th with the Royals.
The only difference I can find is that his glove starts shoulder high while with Colorado, but starts below the waist with KC.
He brings the glove up with his leg in the second video to the point he starts throwing it forward. It may make more moving parts for the hitter to follow, but it is not a ton of change.