Peak Pedro

Pedro_Martinez_ERAData via Baseball-Reference; shows qualifying pitchers only

Pedro Martinez, who was inducted into the Hall of Fame on Sunday, was unparalleled at his peak. After joining the American League in 1998, Martinez threw enough innings to qualify for the ERA title six times; he finished first in four of those years and second in a fifth. Only twice since 1995 has a pitcher led the field in ERA by at least 1.00: Martinez in 1999 (by 1.37), and Martinez in 2000 (by 1.96).

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Vanishing Southpaws

Left_Handed_PitchersData via the Baseball-Reference Play Index

In an insightful analysis today, Matthew Trueblood shows that the share of plate appearances thrown by left-handed pitchers is declining. As seen above, only a quarter of plate appearances have featured a southpaw this year, continuing a three-year downward trend.

The 70s and 80s were the golden age of lefties, who faced at least 30% of batters in every year save for the strike-shortened season of 1981. (Baseball-Reference does not have complete data prior to 1974.) The current rate of 25.1% would be by far the lowest since 1999-2002, when expansion may have made finding quality southpaws difficult.

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Choosing Slides

MLB_Sliders_2010-2015_YankeesData via Fangraphs

Earlier this week, Nick Ashbourne at BP Bronx wrote about the Yankees’ heavy reliance on sliders. As the chart above shows, the Yankees were among the least slider-happy teams five years ago, but their usage of the pitch has spiked this season to 27.0%; if they keep that pace up for the full year, it will be the highest percentage in at least six seasons (surpassing the 2013 Giants at 25.8%). However, as Ashbourne notes, slider usage is correlated with injuries, which is bad news for the already old and injury-prone Bronx.

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Buc-ing a trend

MLB_Sinkers_2010-2015_PiratesData via Baseball Savant

While hurlers across MLB have been throwing fewer sinkers in recent years, the Pirates have increased their usage of the pitch. Per MLBAM’s classifications, 37% of Pittsburgh’s pitches were sinkers (including two-seam fastballs) in 2014, eight percentage points ahead of any other team. The Bucs have ticked down to 35% so far in 2015 (and been surpassed by Oakland), but they are still among the league’s leaders in sinkers.

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Fall of the Sinker?

MLB_Pitch_Types_2010-2015Data via BaseballSavant.com

As a follow-up to yesterday’s chart, here is a graph of aggregate pitch types in MLB since 2010. Pitch selection has been remarkably consistent over time; in 2015, all offspeed pitches are within 0.5% of their usage five years earlier. The exception is the sinker (which includes two-seam fastballs), which has fallen from 25% to 22% since 2010, mostly replaced by four-seam fastballs.

A significant caveat: Most pitch types exist on a spectrum, so MLBAM’s pitch classification algorithm is not perfect — especially for distinguishing between different fastball types. So the apparent decrease in sinkers could reflect changing classifications instead of a change in pitchers’ actual behavior. Additionally, my hypothesis is that the 2013 drop in sliders is due to a classification change (especially given the associated rise in curveballs), since it is out of line with all other years.

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Pitch Selection in MLB

MLB_Pitch_Types_2015Data via BaseballSavant.com

On aggregate, pitchers are throwing mostly the same types of pitches in 2015 as they did last season. The share of curveballs (per MLBAM classifications) has declined by a full percentage point, replaced by a slightly greater share of changeups, fastballs and sliders. Four-seam fastballs remain the most common pitch at about 35%, followed by sinkers (including two-seam fastballs) at 22%.

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