Sophomore Slumps and Surges

It's about time I start geeking it up here at Triple Steal and do some studies. I'll try not to bore anyone with too many tables, or numbers, or thinking. Ross, this is certainly easier for you than actually reading a book.

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I'll start by revisiting a study I did a couple of years ago, trying to determine what factors, if any, you can use to predict which rookies will see continued success in their sophomore season, and which ones will slump. One of Ross's favorite theories is that rookies on playoff teams - rookies who excel in pressure situations - are more likely to be the real deal than rookies who have a nice season in a lower stress environment (say, Kansas City).

I took a look at all rookies since 1980 and pulled out two subgroups: rookies who played for playoff teams (either division winners or the wild card), and rookies who played for teams in fourth place or lower. I ignored rookies who reached their eligibility after their second season (since they're not all that comparable to most rookies) and rookies who split time between two or more teams in their rookie year. (I used the 130 PA requirement to determine which season was the rookie year, since I don't have information about time on the roster.) I only included rookies who also played the following season.

There were 152 playoff rookies in the sample - here's how they hit in their rookie season and in the following year:

Year	AVG	OBP	SLG	PA
Rookie	.270	.336	.404	276
Sophomore	.263	.333	.406	321

Not much of a difference. And there were 512 rookies on bad teams:

Year	AVG	OBP	SLG	PA
Rookie	.256	.318	.389	300
Sophomore	.262	.324	.401	312

The rookies on bad teams improved a bit, although they were worse hitters than the playoff rookies in their rookie season.

Since we don't care much about rookies that didn't get a lot of playing time, let's look at the two groups, looking only at players with at least 400 PA. There were 34 playoff rookies:

Year	AVG	OBP	SLG	PA
Rookie	.281	.350	.422	545
Sophomore	.269	.344	.413	535

And there were 135 rookies on bad teams:

Year	AVG	OBP	SLG	PA
Rookie	.266	.329	.408	510
Sophomore	.266	.331	.415	433

The playoff rookies got slightly worse, while the rookies on bad teams improved slightly. On the other hand, the playoff rookies saw similar playing time in their sophomore season, while the other group lost about 80 PA in their second season. And again, the playoff rookies were just better all around than the rookies on bad teams.

Finally, I'll throw out the very worst of the rookies from the bad teams - the kinds of players that only made the majors because they played for bad teams. This way, the stats of the two groups in the rookie season will be similar. There are now 85 players on bad teams:

Year	AVG	OBP	SLG	PA
Rookie	.276	.346	.427	519
Sophomore	.273	.343	.430	443

There's basically no change. So far, I don't see any evidence that rookies who make the playoffs do better in their sophomore season than similar rookies on bad teams. If anything, the evidence points the other way, since rookies on playoff teams did hit a bit worse in their sophomore season. The only significant difference between the two groups is that rookies on playoff teams had a similar number of plate appearances in their sophomore year, while rookies on bad teams lost some playing time. This may be because bad teams might play some crappy players full-time because they have no other choice, but they cut back their playing time as soon as they can.

Just to make sure age isn't a factor, I checked the average age the players in both groups. Rookies on playoff teams were 24.6 years old and rookies on bad teams were 24.4, so that shouldn't be affecting the results much.

Okay, Ross - tell me why I'm wrong! How can I refine this study?