Prince Fielder of the Milwaukee Brewers came into Monday's action leading the National League in RBI with 42. Driving in runs is often a combination of men on base plus power supplied by the batter, since long hits move runners father along the bases. Slugging percentage represents a distance, the number of bases a player earns in an average at bat. The higher than number, the farther runners on base can advance. Fielder came into the day with a fine .533 slugging percentage.
Fielder's hot zone for power exists in a diagonal from the upper outside corner down the the lower inside corner of the strike zone.
In the past, pitchers worked him away and down as much as possible.
I'm sure pitchers are still trying to replicate this pattern, but so far this year they're getting balls up and in the middle more:
Pitchers are missing their spots, and Fielder is taking advantage of that to drive in plenty of runs. He might slow down a bit as the season progresses and pitchers find their spots against him again.