C.J Wilson (TEX) has had a tough time with close pitches this season. According to PitchFX data, 59 pitches thrown by Wilson could have been called strikes but were not. Four of these pitches came with three balls, resulting in a walk.
Wilson's heat map indicates that the majority of these called balls were on pitches low in the zone.
Umpires tend to have a tougher time consistently calling pitches on the top and bottom of the zone due to the fact that player height slightly alters the zone. Wilson typically locates the majority of his pitches low in the zone, so it's not that surprising to find him near the top of this list.
It's one thing to lose a strike in the middle of a count. However, it hurts a bit more when the missed call comes with two strikes. Here are the leaders for missed called strikes with two strikes on the batter.
Basically, these pitchers missed a chance at notching a strike out looking. Of course, they could have still gotten the K later in the AB. However, the walk column shows how many times they missed a K with a full count. Instead of gaining an out, the missed call resulted in a free base for the opposing team. And in case you're wondering, two players did so with a bases loaded full count this season resulting in a run: Joakim Soria (KC) and Jim Johnson (BAL) walked in one run each due to a pitch called a ball within the strike zone.