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May 27, 2004

Lies, Damned Lies

Southpaw Stories, Part I

by Nate Silver

Two months ago, the Oakland Athletics signed Eric Chavez to a six-year, $66 million contract extension that will keep him with the club through 2010. Despite some head-scratching from the public, there are good reasons behind why Billy Beane campaigned to do for Chavez what he hadn't done for former MVP shortstop Miguel Tejada. Unlike Tejada, Chavez is a player whose skills, like his fine defense and his ever-improving plate discipline, are likely to be undervalued by the market. On top of which, Chavez has continued to demonstrate growth season after season, and PECOTA thinks that he's a very safe bet going forward.

It is no secret, however, that Chavez has a tragic flaw: he can't hit left-handed pitching. From 2001-2003, Chavez managed a stellar line of .306/.375/.579 against right-handers, but a Mathenian .229/.278/.395 against southpaws. The A's, recognizing his defensive value and perhaps hoping that repetition would breed improvement, continued to start him anyway, in spite of a rotating array of viable platoon alternatives.

This year, indeed, has brought about a turnaround--Chavez is crushing lefties so far on the season (.288/.373/.561), while performing well below his career averages against righties (.214/.358/.398). Whether there's any rationale for the change other than sample size, I'm not certain (I don't get to see the West Coast teams play as often as I'd like to). What is clear, however, is that if such a change becomes permanent--if Chavez learns how to hit left-handed pitching at the age of 26--it would be a relatively unprecedented development. In most cases, a platoon split for a left-handed hitter is something like a finger print or a dental record: it remains a readily identifiable and more or less unchanging part of his profile throughout the different stages of his playing life. A left-handed hitter with a big platoon split early in his career is, in all likelihood, going to have a big platoon split later in his career.

Though most folks have been aware of the importance of the platoon advantage for a long, long time, the development patterns of left-handed hitters--particularly left-handed hitters who don't hit left-handed pitchers very well--remains an under-explored subject area. As a result, I'm going to run a three-part series on the issue. Today, we'll look at a sample of historical players, providing a narrative description of the progress of their platoon splits throughout their early and middle careers. In the second part of the series, to run next week or not too long afterward, we'll look at the historical data in a more systematic fashion. I'd like to run a third part to the series, too, describing potential “solutions” to the problem, but that depends on how the second part goes. In the meantime, kids, grab a blanket and a Hi-C: it's time for Southpaw Stories.

Retrosheet has comprehensive data on platoon splits available for each year from 1969 through 1992. There are about 35 left-handed hitters who had their age 22-30 seasons during the era, and who were major league regulars throughout most of that period. I randomly selected a sample of 10 such players to examine further. The lucky contestants are:

• Chris Chambliss
• Keith Hernandez
• Kent Hrbek
• Tony Gwynn
• Ruppert Jones
• Rick Manning
• Al Oliver
• Darryl Strawberry
• Jason Thompson
• Andy Van Slyke