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Control the Zone Redux: The Mariners are emphasizing plate discipline again

Have the Mariners really improved their plate discipline this year?

Houston Astros v Seattle Mariners Photo by Stephen Brashear/Getty Images

Earlier this month, I examined three Mariners hitters who had shown serious improvements to their plate discipline during the first week of the season. Tim Beckham, Domingo Santana, and Ryon Healy are still laying off those pitches thrown out of the zone, but this newfound self-control isn’t just limited to them, it’s a team-wide phenomenon.

If you go down the Mariners lineup, almost every batter has lowered their chase rate (O-Swing%) in 2019, some by significant margins. The three I wrote about earlier are the biggest improvers but Dee Gordon and Mallex Smith have also shaved more than nine points off their chase rate. With so many players showing a discerning eye at the plate this year, it shouldn’t surprise you to see that as a team, the Mariners have dropped six points off their chase rate, from 31.1% in 2018 to 25.1% this year.

This revamped approach at the plate seems to be the result of a renewed commitment to the “Control the Zone” mantra. If you listen to Jerry Dipoto, he’ll say that the team had gotten away from that philosophy last year. “Last year’s group was a fun and exciting offense that ran through hot and cold spells because of a flawed approach. This year’s group has been more sound in their approach.”

But Controlling the Zone isn’t just about laying off pitches out of the zone. Its focus is on coming to the plate with a plan and swinging at the right pitches. That includes a fair amount of patience to wait for those right pitches. Last year, the Mariners were dead last in pitches per plate appearance, seeing just 3.79 pitches on average when a batter came to the plate. This year, they’re seeing 4.12 pitches per plate appearance, the fourth highest mark in the majors.

But their new selective and patient approach at the plate has had some mixed results so far. They’ve increased their walk rate from 7.1% to 8.8% this year, but they’ve also seen an accompanying rise in strikeout rate too. That doesn’t really make sense based on the information above. But being more selective about which pitches to swing at and seeing more pitches per plate appearance are only part of the plate discipline puzzle.

You’re probably aware of the plate discipline metrics listed on FanGraphs like O-Swing%, Z-Contact%, and their brethren. But what’s tricky about these metrics is that they don’t share a common denominator. Some them use total pitches as the denominator but others use pitches in the zone or swings on pitches in the zone. That makes putting these metrics into context fairly difficult. But using the power of math, we can recalculate new metrics that share a common denominator and cover all six possible outcomes for any given pitch. These six outcomes are:

  • Swing and contact made in the zone: (Z-Swing% * Z-Contact% * Zone%)
  • Swing and miss in the zone: (Z-Swing% * (1 – Z-Contact%) * Zone%)
  • Pitch taken in the zone: ((1 – Z-Swing%) * Zone%)
  • Swing and contact made out of the zone: (O-Swing% * O-Contact% * (1 – Zone%))
  • Swing and miss out of the zone: (O-Swing% * (1 – O-Contact%) * (1 – Zone%))
  • Pitch taken out of the zone: ((1 – O-Swing%) * (1 – Zone%))

These six outcomes add up to 100% and give us a more detailed look at a player’s (or team’s) plate discipline. So, what do these revamped plate discipline metrics tell us about the adjustments the Mariners have made this year?

Mariners Component Plate Discipline

Pitch Outcome 2019 2018 Difference
Pitch Outcome 2019 2018 Difference
Swing and miss in the zone 5.2% 3.4% 1.76%
Contact in the zone 24.9% 25.5% -0.62%
Pitch taken in the zone 14.6% 14.2% 0.36%
Swing and miss out of the zone 5.6% 6.5% -0.87%
Contact out of the zone 10.3% 11.2% -0.93%
Pitch taken out of the zone 39.5% 39.2% 0.30%

Here we finally see the biggest change in the Mariners plate discipline and it isn’t a good one. As a team, the Mariners are swinging and missing at pitches in the zone far more often this year. That alone goes a long way towards explaining the increased strikeout rate we’ve seen. We also see that the drop in chase rate has affected both whiffs and contact out of the zone. That’s probably a good thing since making contact on pitches out of the zone usually results in weak batted balls.

There’s only so much we can learn from looking at team-wide trends. It’s more than a little concerning that the Mariners are collectively swinging through pitches in the zone more often, but if it also paired with better quality contact when they do connect, maybe the trade off is worth it. On the surface, it does appear that the Mariners are making better contact this season. Next week, I’ll dig a little deeper into the Statcast data to see if that’s actually the case.