In 2014, Jake Peavy was essentially two different pitchers. With Boston, he couldn’t put anything together, which lead to some very ugly results. With San Francisco, and after making some major adjustments, Peavy regained a semblance of the ace he once was. When Matt Cain fell to elbow surgery for floating bone chips in his pitching arm, the Giants asked Peavy to pick up the slack. What followed was more than anyone could have expected. Peavy was instrumental in getting the Giants to 88 wins to sneak into the playoffs and eventually capture their third World Series in the past five seasons.

The enormous difference between the Peavy in Boston and the Peavy in San Francisco stemmed from two notable changes he made (presumably at the behest of the Giants and their pitching coaches): His pitch selection and his release point. These changes in turn, triggered a cascade of effects that help explain his remarkable turnaround.

Changing Pitch Selection:

Pitch Selection FB% SL% CT% CB% CH% Boston 55.3% 5.7% 16.6% 10.5% 11.9% San Francisco 47.5% 11.3% 20.3% 13.9% 7.0% Percent Change -14.1% 98.2% 22.3% 32.4% -41.2%

Across the board Peavy dramatically shifted how he attacked hitters. He reduced the use of his fastball and replaced it with more sliders and cutters, forcing hitters to deal with more horizontal movement. Throughout 2014, Peavy’s changeup had a negative value, yet it was his third favorite pitch in Boston. In San Francisco however, he gutted his usage of that pitch by 41.2 percent and it became the least used of his five pitches. As his changeup fell to the wayside, he essentially replaced it with his slider, which with San Francisco was used 11.3 percent of the time, compared to his changeup usage of 11.9 percent with Boston.

Changing Release Points:

Peavy has always had an incredibly odd delivery, which served him well in the past. But as the charts below show, leading up to the trade in late July, Peavy’s release point (especially horizontal) on most of his pitches was all over the place. While in Boston, the graph looks like that of seismic activity waves. His enormous trouble with keeping a consistent release point on any of his pitches undoubtedly contributed to his dismal performance with the Red Sox. However once he was traded, the Giants’ pitching coaches were able to help Peavy make the necessary adjustments.

Peavy needed to find consistent release points on his pitches, and as the charts show, he did just that after the trade. In August, September, and October, his release points smoothed out considerably. This is an admittedly small sample size, but that by itself doesn’t nullify what seem to be clear results.

These changes led to great improvements in key areas, specifically in his pitch values and his plate discipline numbers. The Boston Peavy produced negative pitch values for a staggering 72.9 percent of his pitches, but after moving to the Giants, he was able to make dramatic strides.

Pitch Value FB SL CT CB CH Boston -13.6 -2.9 1.2 0.1 -1.7 San Francisco 5.3 3.8 2.1 1.3 -3.7 Point difference 18.9 6.7 0.9 1.2 -2

In Boston, Peavy’s most troubling pitch was his fastball, which was simply atrocious. However after working with the Giants’ pitching coaches, Dave Righetti and Mark Gardner, his fastball became an above average pitch. His changeup, however, went further into the red, and even though Peavy threw it 41.2 percent less than he did with Boston, he couldn’t seem to make an adjustment. Taking all five pitches into consideration, Peavy engineered a remarkable mid-season turnaround, moving from a negative pitch value on 72.9 percent of his pitches as a Red Sox, to producing positive pitch values on 93 percent of his repertoire as a Giant.

With San Francisco, Peavy produced very different plate discipline numbers against hitters, adding to the growing list of stark differences between the Boston Peavy and the San Francisco Peavy.

Plate Discipline O-Swing% Z-Swing% O-Contact% Z-Contact% F-Strike% SwStr% Boston 30.40% 69.40% 67.40% 88.70% 62.30% 8.70% San Francisco 37.30% 73.80% 68.40% 87.50% 68.50% 10.30% Percent Change 22.69% 6.34% 1.48% -1.35% 9.95% 18.39%

While there’s no automatic recipe for success when it comes to plate discipline numbers, we can still use Peavy’s to gain insight into his incredible comeback. In his O-Swing%, there was a 22.7 percent increase in hitters swinging at pitches not located within the defined strike zone. Hitters were chasing Peavy's pitches much more than they were in Boston, which in turn helped raise his SwStr% by 18.4 percent.

Another notable change between the Boston Peavy and the San Francisco Peavy was extraordinary difference between his ISO allowed. With Boston, he was pummeled to the tune of a .201 ISO, a number that Fangraphs considers "great" when coming from a hitter. However with the Giants, his ISO allowed fell to a paltry .104, meaning that hitters were no longer able to punish him for extra bases as much as they used to. This can likely be attributed to the shift in pitch once Peavy had settled in with the Giants.

Peavy focused on the lower part of the strike zone much more so than he did in Boston, and was a strong factor in reducing his ISO allowed.

As we’ve seen, essentially two changes made by Peavy and the Giants’ pitching coaches resulted in some clear-cut differences.

IP K/9 BB/9 HR/9 BABIP LOB% ERA FIP xFIP SIERA Boston 124.0 7.26 3.34 1.45 .301 74.3% 4.72 4.80 4.29 4.24 San Francisco 78.2 6.64 1.94 0.34 .270 76.4% 2.17 3.03 4.01 3.91

The spread among Peavy’s San Francisco ERA, FIP, xFIP, and SIERA suggests that the regression monster will be hungry for him in 2015. While that’s likely true, it’s important to understand why that is. His inflated xFIP can be attributed to Peavy’s incredibly low HR/9 of .34, a career best for him, albeit not for an entire season. It’s probable that in 2015 his HR/9 figure will increase to around his career average of .96, and thus increase his FIP and xFIP, it remains to be seen just how much.

His SIERA of 3.91, while still a marked improvement over his time in Boston, was not great. However this actually makes some sense because of how SIERA is constructed. Fangraphs’ library of metrics indicates that SIERA values strikeouts far more than FIP does. Because of this, Peavy is naturally at a disadvantage in terms of SIERA because he doesn’t strike out that many batters. His K/9 rate of 7.02 in all of 2014, and just 6.64 with San Francisco are below the average of 7.1.

Peavy was an unexpected savior for the Giants during the 2014 regular season. Clearly when the Giants traded for him, they saw something that suggested he could be salvaged, and rewarded him with a 2-year, $24 million dollar contact. While it’s unlikely that he’ll post a full season as good as his twelve starts for San Francisco last season, that doesn’t mean he won’t be valuable. Even as he heads into his age 34 season, if Peavy can sustain the changes that he and the pitching coaches made, there’s a good chance he can still put up above average numbers.

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All statistics courtesy of FanGraphs and Brooks Baseball.

Matt Goldman is a Featured Writer for Beyond the Box Score. You can follow him on Twitter at @TheOriginalBull.