Dexter Fowler (COL) leads the National League in strikeouts with 41, but also comes in second in walks. To rank high in both of those categories, batters need to be fairly selective about what pitches to chase. They not only take pitches outside the strike zone, but also ones inside the zone that they may not handle well.
The Rockies outfielder is a switch hitter, so the following graphs will show him against right-handed pitchers, since he sees those the most. The first heat map shows the general approach pitchers take against Fowler:
Opponents try to work him down and away, and with very good reason:
The place where opponents concentrate their pitches is a black hole for Dexter in terms of getting hits. His pounding the ball on the inside plate gives them good reason to avoid that area as well. Those pitches down and away are in the strike zone, and which means Dexter is often obliged to swing at them:
Now compare that to where he takes pitches:
Dexter will often take the low and away pitches, mostly because he can't hit them. That helps contribute to his strikeouts. He seldom takes the pitch inside, however, because that's where he does damage. Note two that Dexter is extremely good at recognizing the border between a strike and a ball (the solid line represents the rule book strike zone.)
So Dexter is selective in that he is very good at recognizing balls from strikes, but also recognizing pitches he can hit well versus those he can't. The final proof of this is in his .400 BABIP against RHP. When he puts the ball in play, he makes solid contact, and the result is good well beyond the league average.