Pitching
Chase creation
How pitchers earn swings at pitches that finish outside the strike zone.
Explained by Maya Serrano
Player development, pitch design, and roster construction.
A chase is recorded on the pitch that leaves the zone, but it is often built on the pitches that made the zone credible. Count leverage, release similarity, and earlier strikes can turn a takeable ball into a decision the hitter can no longer comfortably pass on. The useful question is not why a hitter swung at a bad pitch. It is what made that pitch look competitive long enough to earn the swing.
Precise definition
Chase creation is the process by which a pitcher earns swings at pitches that finish outside the strike zone—usually after earlier strikes, count pressure, or a strike-like path make the expanded offer look necessary to the hitter.
Why it matters
Chases are usually created by believable strikes, count leverage, tunneling, movement, and hitter expectations rather than by a bad swing appearing from nowhere.
How it works
Credible strikes expand what the hitter must protect
Called or swinging strikes early in the plate appearance teach the hitter that the zone is live. Once protection widens, a pitch that finishes just beyond the edge can draw an offer that would have been taken earlier.
Similar paths make the outside finish believable
Pitches that begin on a strike-like trajectory and break or fade out of the zone are easier to chase than obviously wasted balls. Tracking data can show finish location; it cannot prove the hitter was deceived by a planned tunnel.
Two-strike counts raise the cost of taking a close pitch
With two strikes, taking a pitch near the edge risks a called strikeout. That cost can produce chase swings even when the pitch ultimately finishes outside the zone.
Observable signals
Repeated strikes followed by a similar-looking pitch that finishes outside
What it can mean: Earlier strikes may have widened the hitter's protected area before the chase offer.
Caution: Similarity of path is harder to prove from result labels alone than from full pitch-tracking views.
Two-strike pitches that begin strike-like and finish just beyond the zone
What it can mean: Count leverage may be interacting with location to produce the swing.
Caution: Zone edges depend on the called zone; a chase label is not proof of tunneling.
Elevated first-pitch strike rate preceding later chase offers
What it can mean: Getting ahead can set up later expansion even when the finishing pitch type changes.
Caution: First-pitch strike rate alone does not prove later chase intent or success.
Illustrative example
Illustrative expansion before an outside finish
Illustrative teaching sequence, not a real game. A right-handed hitter faces a pitcher who has already thrown two competitive strikes.
Step 1
First-pitch strike
Observation: A fastball is taken for a called strike on the outer third.
Interpretation: The hitter has seen a live outer-third strike and must respect that edge.
Step 2
Second strike in a similar lane
Observation: Another pitch lands near the same outer third for strike two, fouled off.
Interpretation: Protection around that lane has been reinforced before any chase pitch appears.
Step 3
Similar look finishes outside
Observation: A breaking pitch begins on a comparable path but finishes below and outside the zone; the hitter swings and misses.
Interpretation: The chase is readable after the expanded protection, not as a free-standing bad swing.
Takeaway: Chase creation is usually prepared by credible strikes and count pressure before the outside finish arrives.
Limitation: This invented sequence cannot prove tunneling, catcher targeting, or that the pitcher intended the expansion.
Common misinterpretations
Mistake: Calling every chase a tunneling masterpiece.
Better reading: Separate the observed finish outside the zone from claims about identical release tunnels or pitcher intent.
Mistake: Treating chase rate as a pure measure of pitcher skill.
Better reading: Chase rates also reflect umpire zones, hitter aggression, count mix, and sample size.
Metrics and limitations
- Chase rate
Measures: The share of pitches outside the zone on which the hitter swings.
Useful for: Summarizing how often hitters offer at non-strikes against a pitcher or in a count.
What it misses: Does not prove tunneling or intent; depends on zone definition, pitch mix, and hitter quality.
- Zone rate
Measures: The share of pitches that finish inside the strike zone.
Useful for: Checking whether chase opportunities sit beside a diet of competitive strikes.
What it misses: Zone rate alone cannot show whether outside pitches looked like strikes in flight.
- First-pitch strike rate
Measures: How often the first pitch of a plate appearance is a strike.
Useful for: Seeing whether pitchers regularly create early count leverage before later expansion.
What it misses: Getting ahead does not by itself prove later chase creation or explain any single swing.
- Two-strike chase rate
Measures: Chase rate restricted to two-strike counts.
Useful for: Focusing on the counts where protection and expansion most often meet.
What it misses: Still cannot separate pitcher craft from hitter protectiveness or umpire zone effects.