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Two years ago Mike Fast (now with the Houston Astros) took a look at pitchers who gained or lost velocity between the end of 2010 and spring 2011. We won't summarize his whole study here, but here’s the money quote:

There is definitely a predictive relationship between the fastball speed change observed in spring training and the fastball speed change observed in the regular season. Pitchers on average retained 41% of their spring training speed changes into the regular season, and the correlation coefficient for the sample here is r=0.53.

With that predictive relationship in mind, we've compared velocities from September 2012 and March 2013 and come up with some interesting results. This year's study includes World Baseball Classic pitchers, who were all limited in their usage by rule.

First, a summary of gainers and losers:

Total Pitchers

69

Gainers

25

Losers

44

Average Change

-0.4 mph

MPH Change

# of Pitchers

3

1

2

0

1

6

0 to 1

18

-1 to 0

24

-1

14

-2

5

-3

1

Most pitchers didn't change much at all, with 42 guys within one mile per hour of their September velocity one way or the other. There were more losers than gainers (44 to 25), with 20 guys losing at least one mph but only seven gaining that much.

The pitchers listed below each threw at least 20 fastballs or sinkers (combined) in both September 2012 and March 2013 as a starting pitcher. (Pitches thrown in relief by pitchers who also worked out of the bullpen were not considered.) The big table below shows the raw speed numbers and the change between the two periods. In addition, we reran the numbers using Mike's temperature adjustment technique (37 degrees = 1 mph fastball velocity change, baselining from 70 degrees) and recalculated the changes between periods. For sanity's sake we're showing only the raw numbers below, along with the “Delta” and “DeltaAdj”, the latter being based on the adjusted speed numbers.

Pitcher

SEP12

MAR13

Delta

DeltaAdj

Andrew Cashner

93.0

96.3

3.3

3.0

Patrick Corbin

91.3

93.2

2.0

1.7

Jarrod Parker

93.6

95.2

1.6

1.6

Homer Bailey

92.4

94.2

1.8

1.5

Kyle Kendrick

89.9

90.5

0.6

1.2

Luke Hochevar

93.1

94.3

1.2

1.1

Travis Wood

89.2

90.4

1.1

1.1

Jason Vargas

88.7

89.5

0.7

0.9

Madison Bumgarner

90.7

91.6

1.0

0.8

Jake Peavy

91.5

92.1

0.6

0.7

Ubaldo Jimenez

91.8

92.7

0.9

0.7

Tim Lincecum

90.4

91.0

0.6

0.6

Josh Beckett

91.5

91.6

0.1

0.6

Derek Holland

94.1

94.4

0.4

0.5

Edinson Volquez

93.8

93.9

0.1

0.4

Yu Darvish

93.9

94.2

0.3

0.3

Andy Pettitte

88.9

88.9

-0.1

0.3

Blake Beavan

90.8

91.3

0.6

0.3

Trevor Cahill

90.4

90.8

0.4

0.2

Bud Norris

92.2

92.3

0.2

0.2

Mike Fiers

88.9

89.1

0.3

0.2

Gio Gonzalez

93.5

93.7

0.2

0.1

Aaron Harang

90.2

90.4

0.2

0.1

Edwin Jackson

94.5

94.6

0.1

0.1

Ervin Santana

91.6

91.8

0.2

0.0

Mark Buehrle

85.6

84.9

-0.7

0.0

Ian Kennedy

90.2

90.1

-0.1

-0.1

Chris Sale

91.2

91.3

0.1

-0.1

Marco Estrada

90.7

90.4

-0.3

-0.2

Tommy Hanson

89.9

89.4

-0.5

-0.2

Mat Latos

93.2

92.8

-0.4

-0.3

Josh Johnson

93.5

92.6

-1.0

-0.3

Zack Greinke

92.9

92.5

-0.4

-0.4

Wandy Rodriguez

90.4

90.2

-0.3

-0.4

Matt Harrison

92.8

92.4

-0.4

-0.4

Barry Zito

84.5

84.1

-0.4

-0.6

Clayton Kershaw

93.8

93.3

-0.4

-0.6

Eric Stults

88.2

87.5

-0.7

-0.6

William Smith

90.3

90.1

-0.2

-0.7

Bronson Arroyo

87.9

87.4

-0.5

-0.7

Dan Straily

92.0

90.9

-1.0

-0.7

Hector Santiago

93.8

93.0

-0.8

-0.7

Jeff Samardzija

96.2

95.6

-0.5

-0.8

James Shields

93.8

93.4

-0.5

-0.8

Yovani Gallardo

92.4

91.4

-1.0

-0.9

Hisashi Iwakuma

90.6

90.1

-0.5

-0.9

Jordan Zimmermann

94.9

93.3

-1.6

-0.9

Scott Feldman

92.1

91.0

-1.0

-1.0

Tommy Milone

88.8

87.5

-1.2

-1.0

Chris Capuano

89.0

87.9

-1.1

-1.2

Wade Miley

91.2

90.1

-1.1

-1.2

Luis Mendoza

92.7

91.8

-1.0

-1.2

Samuel Deduno

91.7

90.2

-1.5

-1.2

Cliff Lee

92.3

90.2

-2.0

-1.3

Clayton Richard

90.7

89.6

-1.1

-1.3

Zach Stewart

89.5

88.6

-0.9

-1.3

Jerome Williams

93.7

92.5

-1.2

-1.4

Tyler Chatwood

94.4

93.1

-1.3

-1.4

Matt Moore

94.2

92.5

-1.7

-1.6

A.J. Griffin

90.5

88.8

-1.7

-1.6

Jeremy Guthrie

93.3

91.9

-1.5

-1.7

Joe Saunders

88.6

87.2

-1.4

-1.8

Doug Fister

90.0

88.2

-1.9

-1.9

Joe Blanton

91.2

89.0

-2.2

-2.0

Bruce Chen

87.2

85.1

-2.1

-2.1

Felix Hernandez

93.6

91.7

-1.9

-2.2

Justin Masterson

94.1

91.7

-2.4

-2.6

Wily Peralta

96.3

93.4

-2.9

-2.8

Ryan Vogelsong

92.7

89.5

-3.2

-3.2

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BuzzingThalami
4/01
Good stuff! Wish there were data on more pitchers. Would love to see Halladay's, for instance.