Sophomore slump

From BR Bullpen

When a player declines after their rookie season, it is called a sophomore slump. A sophomore slump is far from universal. As pitchers tend to fare worse when exposed to the same hitters multiple teams, a sophomore slump is not unusual. Additionally, a hitter may get regular playing time when they are on a hot roll and the law of averages would indicate that they would decline with increased time - for instance, Chris Duffy hit much better in a limited sample with the 2005 Pirates than his minor league track record would indicate. This earned him a regular role - in 2006, he declined as would be expected for someone playing over their head. People judging him on 2005 alone and ignoring his minor league statistics then call this a sophomore slump.