The "sophomore slump" really does exist.
Just ask Atlanta's Jason Heyward, Detroit's Austin Jackson or Ivan Nova of the New York Yankees—three of the more recent examples of players who wowed us as rookies only to slump badly during their second year in the show.
My first introduction to the phenomenon came in seventh grade, when a friend of mine did his science project on the "sophomore slump." Back then, he used batting average and ERA for comparison, as this was well before the advent of sabermetrics.
With that in mind, I decided to take a look at the 99 players who have received votes for their league's respective Rookie of the Year award since 2006—58 position players and 41 pitchers—using OPS and ERA as a basis for comparison.
Of the position players, only 17 saw their OPS increase in their second season, and only five saw it rise by at least 100 points. Prince Fielder leads that group, going from an OPS of .831 in 2006 to a 1.013 mark in 2007.
On the mound, 11 pitchers produced lower ERA's as sophomores than they did as rookies, with four dropping their ERA's by at least a full run. Daisuke Matsuzaka is the ace of the group, going from a 4.40 ERA in 2007 to a 2.90 in 2008.
That works out to nearly 72 percent of those who received a vote over the past six seasons producing a lower OPS or higher ERA as sophomores than they did as freshmen.
Can last year's group of Rookie of the Year candidates buck the trend, or are they doomed to repeat history?
Let's take a look at how they're doing in the early goings of their sophomore seasons and see if there are any warning signs that we should take note of.
*Unless otherwise noted, all statistics courtesy of Baseball-Reference.com.