Much has been written about Mike Pelfrey's great start to 2010, and there have been any number of articles on the reasons why.
Many attribute it to confidence, having a personal catcher in Henry Blanco, better physical condition, his marriage, or simple maturity.
Whatever the reasons, we can certainly see the results when we compare his April 2009 to his April 2010.
Let's look at his pattern from the called strike zone side by side:
The first of the two pictures is his April 2009 called strikes.
As you can see, there is pretty wide pattern in 2009, with many pitches way outside of the zone, giving the batter ample opportunity to make his "non-swing" decision.
Additionally, the edge of the strike zone, where most pitcher's live, is ignored, especially the "up and in" or "up and away "spots that are the natural weaknesses of many hitters.
Now let's compare it to his April 2010 called strike zone.
In 2010, we see a much tighter pattern, and many more pitches an inch or less outside of the zone. This shortens the batter's reaction time, and the results can be seen in many more called strikes. Additionally it certainly appears that Pelf is working both the bottom of the zone, as he usually does, but more importantly he is working the up and in and up and away zones with much more frequency.
Bottom line--Pelfrey's control is tremendous right now, he is using all parts of the plate, and he is certainly pitching like an Ace.