June 30, 2009

Statman's Notebook

Matched Pairs

by Eric Seidman

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Welcome to the inaugural entry of the Statman's Notebook, an every-so-often entry in which fun facts and relatively useless information will be tossed around with abandon, allowing data to be employed in a not-so-hardcore manner. The goal here is to have some fun with numbers and player performance, so ideas for research are always more than welcome. Our topic this week is a portrait of slash-line consistency placed in a 21^st-century Jayson Werth-style frame. Werth, the Phillies outfielder who began his big-league career with the Blue Jays, had himself a mighty productive weekend in Toronto, substantially increasing each component of his triple-slash rates line. After a .750/.786/1.625 showing, complete with his reaching base safely in 11 consecutive trips to the plate, Werth's .257/.344/.460 season had been transformed into .271/.364/.494.

Why is this noteworthy? Well, his season-ending line from 2008 read .273/.363/.498. Now, through 313 plate appearances this season, Werth has a virtually identical line. Granted, past performance does not always point to what we should expect moving forward, but it seems pretty cool to me in a very nerdy way that his current level of slash productivity is essentially no different than his bottom line from a year ago.

Curious about this Seidman-proclaimed phenomenon, I decided to investigate how often, if ever, this has occurred. Our time span of choice is the post-strike era, ranging from 1996-2008. The process began with the calculation in my database of running totals and averages for each hitter after each game in every one of those seasons. Much like the balance sheet of a company, this query provided snapshots of performance at specific points in time. These progressive tallies were then compared to the slash lines posted the year before, and then filtered to limit the results to instances in which a player had accrued 250 or more plate appearances in a season, while hovering within three points on each side of the three slash-line components in the previous season.

As an example of the results in action, Joe Crede hit .239/.299/.418 in 2004, and sported a .239/.300/.417 line through 257 plate appearances the very next year. Overall, 197 rows were returned consisting of 69 distinct players and 72 player-seasons. The discrepancy between rows and player-seasons can be attributed to multiple instances occurring for an individual in a specific season. The entire list was then filtered to only include instances wherein the slash lines rose or fell no more than one point from the year prior. All told, 25 rows were returned, comprised of 15 player-seasons. Only eight of these instances-all produced by unique players-involved identical marks in two areas, with a mere one-point discrepancy in the third:

                         First Year        Second Year
Player          Years    AVG/ OBP/ SLG     PA   AVG/ OBP/ SLG
Emil Brown     2005-06  .286/.349/.455    462  .286/.348/.455
Ryan Garko     2006-07  .292/.359/.470    470  .292/.360/.470
Chris Gomez    2001-02  .259/.298/.402    382  .259/.298/.401
Juan Gonzalez  1997-98  .296/.335/.589    364  .296/.335/.590
Carlos Lee     2006-07  .300/.355/.540    493  .300/.355/.539
Damian Miller  2004-05  .272/.339/.403    422  .271/.339/.403
Neifi Perez    2000-01  .287/.314/.427    449  .288/.314/.427
Juan Pierre    2002-03  .287/.332/.343    331  .287/.332/.343

You may notice that the final member of this list held steady in all three categories. Yes, Juan Pierre is the only player since 1996 to post a slash line in at least 250 plate appearances that is identical-to three decimal places-to the previous season's. Of the other seven players featured in the table, Carlos Lee had reached his "matched pair" at the latest seasonal juncture, 493 plate appearances into his 2007 campaign. Pierre's 331 plate appearances in the 2003 season are actually the lowest total of these eight players.

Interestingly enough, some of the players with multiple instances did not post their strikingly similar lines in consecutive games. Chris Gomez hit .259/.298/.402 in the 2001 season, and found himself with a .260/.299/.401 line through 371 plate appearances the next season; a .259/.298/.401 line through 382 plate appearances; and a .260/.298/.403 line through 393 plate appearances. Likewise, Jim Edmonds boasted a gaudy .304/.410/.564 line in the same 2001 season, but actually saw 10 plate appearances pass between the two instances in which he closely matched that line the following season. Neifi Perez, on the other hand, did come close in consecutive games, coming within a point of all three components through 435, 440, 445, 449, and 455 plate appearances in 2001.

Jayson Werth may very well finish the season with a line unrecognizable to that of a year ago, but right now, his marks are essentially right in step with his level of production at the end of the 2008 season, a feat which is much more common than you might think, but still relatively rare.

Eric Seidman is an author of Baseball Prospectus. 
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