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.