When an MLB player turns in a big season these days, the immediate question is whether it is something he is capable of duplicating—and with so many advanced stats available, regression is becoming easier to project.
For hitters, an unusually high batting average on balls in play (BABIP) is a good sign that a high batting average is not sustainable. With sluggers, a spike in home-run/fly-ball percentage could mean that their unusually high home-run total was the result of some good luck.
With pitchers, BABIP and fielding independent pitching (FIP) are good gauges of what kind of fortune they had the previous season. Things like average fastball velocity can also be a tip-off of declining stuff.
What follows is a look at 10 players who enjoyed very good seasons in 2013 but, for one reason or another, look to be in line for noticeable regression in 2014.