I was looking back at THT Baseball Annual 2006 this weekend and compared the lists of 25 players who under and overperformed their prOPS in 2005. The article claimed that the overperformers were likely to “take a step backwards in 2006” , while the underperformers “will progress towards their previous form in 2006”.
Didn’t seem to work out that way. Of the 25 overperformers, just 13 regressed. Of the 25 underperformers, just 13 progressed. Looks to be about the same as flipping a coin. Could be this is just too small a sample to test prOPS. Could be that the findings in the article were based on 3 year prOPS, and one year data is too unstable to predict. In any case, one year prOPS does not look reliable enough to project who will progress/regress the next year.