Jacob Peterson, one of my esteemed colleagues at Beyond the Box Score, has a fantastic post up today in which he introduces new ways to measure hitters’ passiveness (defined as how often a batter takes pitches in the strike zone) and aggressiveness (how often he swings at balls out of the zone). According to his calculations, Michael Brantley is one of the most passive hitters in the league.
Using Baseball Prospectus’ plate discipline statistics, Peterson came up with the following equation for passivity:
"Passiveness = (1 – Z-Swing%) * Zone%"
Or, in other words, if a batter sees 100 pitches, his Passiveness percent is the number of pitches that would be called strikes. Aggressiveness (calculated similarly with O-Swing%) would be the amount of would-be balls that the batter chases.
There were 289 MLB hitters who saw at least 1,000 pitches in 2011, and of those Brantley ranks sixth with 26.3 “passive takes” per 100 pitches seen, behind only Brett Gardner, Marco Scutaro, Jamey Carroll, Maicer Izturis, and Alexi Casilla. Immediately following him on the list are Bobby Abreu, Denard Span, Ryan Hanigan and Sam Fuld to round out the Top 10.
A high passiveness isn’t necessarily a good or a bad thing—letting hittable pitches go by doesn’t help, but a selective hitter knows that he can’t necessarily hit every pitch that’s over the plate—but Peterson notes that no dominant hitters rank highly in it. Brantley doesn’t have phenomenal plate discipline, but he’s solid at least and his aggressiveness is only 10.6%.
Another interesting finding Peterson made: at a combined 29.2% (13.5% passive, 15.6% aggressive), Matt LaPorta the 15th-least passive aggressive hitter in baseball. In other words, he swings at most strikes and takes most balls. For obvious reasons, hitters who do well in this category tend to be very good, as a low passive-aggressiveness shows strong strike zone judgment. That’s at least a somewhat encouraging sign.