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Wednesday, April 04, 2007

Selection Pressure

In my column tomorrow on Baseball Prospectus I chronicle the decline of Angel Berroa in an article titled "In the Arms of an Angel". After summarizing Berroa's tenure since coming into the Royals system in the Johnny Damon trade, I do a little analysis to document players who, like Berroa, had three straight years of decreasing productivity while in their prime and retaining their regular jobs. I did this by looking at OPS park adjusted and normalized by league for players between the ages of 24 and 30 while garnering 400 or more plate appearances.

It turns out that has happened 96 times in baseball history for 85 different players. Those 96 instances are shown in the table below sorted by primary position of the player in their first year (the second year would be the first year of the decline) and NOPS/PF in that first year. You'll then see their NOPS/PF for each subsequent season and the average decline per year calculated using the geometric mean. The list is sorted by position since a shortstop has a greater probability of keeping his job even in an offensive decline given that his defense is more important and therefore a good defender will see less selection pressure applied to his offense.


NOPS/PF
Name Yr1POS Yr1Age Year1 Year1 Year2 Year3 Year4 Avg
Jimmie Foxx 1B 24 1932 160 157 150 147 2.6%
Lou Gehrig 1B 27 1930 158 155 147 145 2.4%
Norm Cash 1B 26 1961 157 123 122 115 4.7%
Jimmie Foxx 1B 25 1933 157 150 147 133 4.4%
Jimmie Foxx 1B 26 1934 150 147 133 119 5.9%
Andres Galarraga 1B 27 1988 130 111 104 88 11.2%
Keith Hernandez 1B 25 1979 130 128 124 116 3.1%
Eddie Murray 1B 27 1983 129 128 126 118 2.0%
Gregg Jefferies 1B 25 1993 124 119 106 101 5.9%
Sean Casey 1B 24 1999 123 113 110 90 7.3%
Gregg Jefferies 1B 26 1994 119 106 101 98 5.3%
Willie Upshaw 1B 26 1983 118 110 106 95 6.3%
Steve Balboni 1B 27 1984 112 107 99 91 6.5%
Willie Upshaw 1B 27 1984 110 106 95 93 4.3%
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Eddie Collins 2B 27 1914 145 137 124 118 6.3%
Larry Doyle 2B 24 1911 133 121 111 110 4.1%
Jimmy Williams 2B 24 1901 125 122 109 107 3.6%
Jimmy Williams 2B 25 1902 122 109 107 102 4.5%
Frankie Frisch 2B 24 1923 121 120 114 107 2.9%
Bret Boone 2B 25 1994 116 104 86 85 5.9%
Carlos Baerga 2B 24 1993 113 110 105 88 5.8%
Tony Cuccinello 2B 27 1935 112 111 110 104 1.6%
Damion Easley 2B 27 1997 110 104 99 98 3.0%
Marty McManus 2B 24 1924 110 105 102 101 2.3%
Billy Goodman 2B 27 1953 108 101 100 98 2.3%
Dick Egan 2B 25 1909 107 94 92 89 4.4%
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Eddie Mathews 3B 27 1959 142 139 132 124 4.0%
Heinie Zimmerman 3B 25 1912 140 129 116 107 8.5%
Richie Hebner 3B 24 1972 132 120 119 103 4.7%
Tommy Leach 3B 24 1902 121 115 103 101 4.6%
Richie Hebner 3B 25 1973 120 119 103 101 2.8%
Max Alvis 3B 25 1963 115 110 103 101 3.8%
Kevin Seitzer 3B 25 1987 114 110 102 101 2.9%
Bill Mueller 3B 26 1997 109 107 104 97 3.3%
Bobby Byrne 3B 27 1912 109 98 96 84 6.4%
Eddie Foster 3B 27 1914 108 104 102 93 4.0%
Bill Coughlin 3B 26 1905 102 95 92 83 6.0%
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Mike Scioscia C 26 1985 121 104 98 97 4.4%
Gus Triandos C 27 1958 114 109 107 104 2.8%
Manny Sanguillen C 27 1971 113 108 104 101 3.6%
Rick Ferrell C 25 1931 109 107 106 101 2.0%
Sammy White C 24 1953 102 99 96 82 5.1%
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Ken Griffey CF 27 1997 135 127 121 118 4.1%
Raul Mondesi CF 27 1998 114 108 107 101 3.0%
Brian Hunter CF 25 1996 94 90 82 73 7.5%
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Bobby Higginson LF 25 1996 125 118 108 94 8.5%
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Ty Cobb OF 25 1912 156 154 152 147 1.8%
Ty Cobb OF 26 1913 154 152 147 144 2.1%
Kevin Mitchell OF 27 1989 153 131 126 108 9.2%
Tris Speaker OF 24 1912 149 147 145 130 2.7%
Albert Belle OF 27 1994 148 142 130 109 8.2%
Bobby Murcer OF 25 1971 147 141 118 105 9.0%
Joe Medwick OF 25 1937 147 125 119 118 3.9%
Tito Francona OF 25 1959 142 118 116 103 6.8%
Duke Snider OF 27 1954 142 140 133 126 3.3%
Edd Roush OF 24 1917 136 131 128 125 2.7%
Tony Oliva OF 25 1964 131 126 123 119 3.1%
Mike Greenwell OF 24 1988 130 112 109 104 5.5%
Jim Rice OF 25 1978 130 128 112 109 3.7%
Steve Kemp OF 24 1979 125 116 115 111 2.8%
Kirk Gibson OF 27 1984 123 122 117 116 1.4%
Tom Tresh OF 27 1965 123 115 106 98 7.3%
Jim Russell OF 25 1944 123 115 110 99 6.6%
Al Smith OF 27 1955 121 110 104 103 3.6%
Greasy Neale OF 25 1917 120 110 100 95 7.2%
Carl Furillo OF 27 1949 119 110 107 94 6.3%
Amos Otis OF 25 1972 118 115 110 101 4.5%
Tito Francona OF 26 1960 118 116 103 93 5.7%
Phil Bradley OF 26 1985 117 114 109 108 2.2%
Steve Kemp OF 25 1980 116 115 111 101 3.0%
Paul Blair OF 25 1969 116 111 104 96 5.9%
Gus Bell OF 26 1955 116 115 101 93 4.4%
Jack Smith OF 26 1921 115 113 106 97 4.5%
Jackie Brandt OF 27 1961 114 111 103 97 4.8%
Luis Polonia OF 26 1990 112 101 94 86 8.3%
Mule Haas OF 27 1931 111 102 101 93 4.0%
Marty Cordova OF 25 1995 110 106 96 92 5.2%
Marquis Grissom OF 25 1992 110 107 103 93 4.6%
Don Mueller OF 27 1954 108 98 86 83 7.3%
Joe Vosmik OF 27 1937 107 105 96 94 3.2%
Devon White OF 24 1987 101 97 93 90 3.7%
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Raul Mondesi RF 26 1997 127 114 108 107 3.7%
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Alex Rodriguez SS 24 2000 136 134 127 125 2.3%
Robin Yount SS 26 1982 135 127 113 107 7.0%
Alex Rodriguez SS 25 2001 134 127 125 117 3.7%
Barry Larkin SS 27 1991 126 120 116 107 5.0%
Ray Chapman SS 26 1917 119 111 109 108 2.2%
Travis Fryman SS 24 1993 117 103 98 97 3.9%
Freddy Parent SS 27 1903 117 115 95 93 4.0%
Jeff Blauser SS 26 1992 116 115 94 89 4.4%
Jay Bell SS 27 1993 115 106 99 96 5.4%
Jody Reed SS 26 1989 106 104 99 87 4.8%
Chick Galloway SS 25 1922 106 94 87 79 9.2%
Rafael Ramirez SS 24 1982 99 98 87 85 3.0%
Angel Berroa SS 25 2003 98 92 90 73 6.3%
Bud Harrelson SS 25 1969 93 92 91 86 1.9%


What you'll notice of course is that all but four of these declines started with the hitter having an NOPS/PF greater than 100. As you might expect, players can retain their jobs through performance declines typically only if that decline starts from a fairly high plateau. Overall, the average of the first year is 123 and the fourth 104. You'll find Berroa second from the bottom as only Bud Harrelson began from a lower NOPS and retained his job through three years of decline. But you'll also notice that Berroa's decline averaged 6.3% while Harrelson was fairly steady at 1.9%.

The bottom line is that Berroa's ability to keep his job was pretty much unprecedented given his offensive performance and even more incredible given that under John Dewan's Plus/Minus system and the data shared by The Hardball Times he fielded 84 fewer balls than would have been expected.

Major League players are under a great deal of selection pressure akin to what organisms feel ala natural selection. Berroa didn't feel it nearly as acutely as he probably should have.

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