On September 1st 2009, Jose Bautista had 49 career home runs to his name, or roughly one for every 40 times he stepped to the plate. In the 31 months of baseball since, Bautista has mashed 237 home runs, or roughly one for every 16 times he has stepped to the plate. And that's obviously been the catalyst in Bautista's transformation from a below average career hitter on that date (88 wRC+) to one of the best in baseball (156 wRC+).
But home runs are far from only thing he turned around. Before the breakout, Bautista 1.0 struck out 21.6% of the time, which he's since cut down to 16.2%. So Bautista 2.0 has reduced his strikeout rate by 24%, despite overall strikeouts actually rising from 16-17% to around 19%. Likewise, he's drawing a lot more walks. Bautista 1.0 drew non-intentional walks 10.7% of the time. That's increased to 14.7% for Bautista 2.0, a 38% increase that turned a modest strength into huge outperformance.
It turns out that these improvements in walk- and strikeout-rate are very significant factors in Bautista's increased production. By my math, of the overall 68 point increase in wRC+, about 47 points are due to the increase in home runs home runs, but walks and strikeouts combine for 26 points, which changes in other all events actually having a modest -5 impact.
The adjustments that Bautista made to allow him to tap into his power have been well-documented and explain the increase in power output. But one third of his increased production is on events that don't involve balls in play, though obviously pitchers would be more careful and reticent to come into the zone. And this is evident in looking at the trend in the Zone% of pitches thrown to Bautista from year to year: formerly in the low-50s, now in the low-40s. But that's just one factor that influences strikeout and walk rates, in addition to factors such as pitch recognition/batting eye, swing rate (patience), and contact rate. And that's to say nothing of those factors compounding each other.
So did Bautista also change his approach, or improve one of these skills. Since 2008, pitch by pitch data is available from Pitchf/x. I downloaded that from the inimitable Baseball Savant, and compiled 2004-07 data myself in order to get a better sense of how this happened.
Contact rate (avoiding swings and misses) is the single most important factor to predict strike out rate, since roughly 75% of all strikeouts are swinging. It also has a small impact on walk rate, since avoiding whiffs can keep at-bats alive. In particular, two strike contact rate is what really matters (to the extent it differs from overall contact rate).
Prior to his breakout, Bautista missed 21% of the time he swung (79% contact rate). Since then, he's come up empty 20.3%. This is slight improvement, but not enough to explain his decrease in strikeouts swinging from 14% to 11.7%. But there is one interesting change. When in a deep hole (0-2 or 1-2), Bautista has lowered his swing and miss rate from 24% to 19%, though his overall rate with two strikes is down more modestly from 20.5% to 18%. But this actually accounts for most of the decline in strikeout swinging. As the increased contact is limited to two strikes, this appears to more a change in two strike approach then ability.
Taking pitches and working the count is often associated with the ability to draw walks (though can also lead to more strikeouts), and Bautista is well known as a patient hitter. Across the league, batters take about 54% of pitches, including about 72% of first pitches. Bautista on the other hand takes about 61% of pitches, and 79% of first pitches, or about 7% on both. Across the board, that ~7% margin compared to the league is very consistent.
But that was also true of Bautista 1.0, as he took 60% of pitches and 80% of first pitches even back then. With no strikes, it was 25% then, 24% now; with two strikes 57% to 56% (which is about the only time he gets within 5% of the league rate). So we can safely rule this out is a significant factor in his improved plate discipline.
This is where things get more complex. As stated above, batters, take about 54% of pitches, and that breaks down into 36% balls to 18% called strikes, so roughly a 2:1 ratio. For Bautista 1.0, that ratio was 39% balls to 21% called strikes. Both were higher because he took so many pitches, but the extra 3% balls for 3% called strikes was not a good tradeoff. It was even worse on first pitches, where Bautista has a 42%/38% split, with th eleague around 39%/33%. He took more pitches, but fell behind.
It's been a different story entirely for Bautista 2.0. Overall, he has 42% pitches called balls, compared to 19% called strikes. That's 6% more balls, but only 1% more strikes, which is a great tradeoff. The same is true on first pitches, and across the board.
Does this reflect an improved batting eye or just seeing more balls out of the zone that are being taken? It's a chicken-and-egg problem, but considering Bautista is still taking pitches at the same (high) rate, it seems to me it's more likely that the latter. Pitchers did not much fear Bautista 1.0, so they pounded the zone, also knowing his proclivity to take pitches would tend to result in him falling behind. Incidentally, this is not to say that Bautista lacks a good batting eye, just that it has not improved and been a catalyst for better outcomes.
Either way, this shift of roughly 3% of pitches from called strikes to balls has a surprisingly large impact on plate discipline results, especially for longer plate appearances where the 3% difference compounds. Fewer called strikes lowers the number called strikeouts, but it means fewer two strike counts and thus fewer opportunities to strikeout in the first place (called or swinging). It's why Bautista now strikes out looking 50% less often at 4.5% instead of 7.3%. Likewise, it meas getting to a lot more three-ball counts, which is a necessary condition to walking.
In recent years, Bautista appears to have tweaked his two strike approach which has helped improve his plate discipline metrics, but the main factor appears to be that increased respect for his power has resulted in more balls out of the zone, which complements his patient approach resulting in improved It also has created a virtuous cycle: more power leads to more balls out of the zone, leads to more balls taken, which allows him to sit on pitches and increase the chance of launching balls.
There's a broader implication: the AL East and Rogers Centre are conducive to power, and the Jays have had success with getting reclamation projects to tap into power. For players with the right skill set at the plate, improved power can drive improved plate discipline production (see: Encarnacion, Edwin) but it won't apply across the board (see Francisco, Juan).