The major challenge of the first couple of months for teams, fans and fantasy players is sorting out what changes in player performances are the result of changes in underlying skill and what are the result of good or bad luck. With only 10 or so starts behind most pitchers, a few runs saved or lost because of good or bad bounces or defensive plays can swing an ERA by upward of a run. So luck can have a major impact on our perception of players.
Baseball Info Solutions tackles that challenge with its defense-independent pitching statistics (DIPS), which compare pitchers' batted balls allowed to similar batted balls in recent seasons based on their velocity and trajectory. DIPS then credits pitchers based on the frequency of results of those similar plays.
For example, Jon Lester could allow a hard-hit line drive to deep right field, and if Jason Heyward makes a spectacular play to catch it, Lester will have earned an out. In DIPS, instead of an out, Lester would receive something like 0.8 doubles, 0.1 triples and 0.1 outs, the average result of similar balls in play.
Occasionally, pitchers can maintain big differences between their actual results and their DIPS over the course of a season, most often if they play in front of a really good or bad defense or play in an extreme pitcher- or hitter-friendly park. However, more often than not, pitchers who show a big difference over the first two months will have their actual results regress to their DIPS expectations as they pitch more innings. Because of that, we can use DIPS to judge whether pitchers who have performed poorly so far this season have been hurt by poor luck and should rebound over the rest of the season.
Let's start with a few pitchers who should bounce back.