Willson Contreras turned more borderline pitches into strikes as the the second half of the 2019 season progressed, but his improvement extended beyond earning called strikes for his pitchers. In addition to influencing umpires’ calls, Contreras’ quieter framing resulted in more swings at breaking pitches.
Specifically, Cubs starting pitchers induced twice as many swings in the lower-left corner of the zone in the second half with Contreras behind the plate.
This aligns perfectly with refined pitch framing, as the ability to steal more streaks likely nudged batters to swing at more pitches due to the anticipation of such called strikes. The regions in which batters swung at more breaking pitches are the same in which Contreras earned more strikes. Most notably, we see a massive increase in called strikes on pitches up in the zone.
Pitch framing is now a quantifiable trait, but its effects beyond called strikes are difficult to calculate. So while Contreras gets credit for earning his starters called strikes on breaking pitches, his efforts to induce more swings on breaking pitches will just have to remain our little secret for the time being.