Over the last 10 or so seasons, this has been the time of the year when we’ve listed a group of players we expect to see a power breakout in the upcoming regular season. That list is based on a study of players from 1996-2001 that saw players who saw an increase in their spring slugging percentage of at least 100 points over their career slugging percentages entering the season then increase their slugging percentage in the regular season relative to their previous career levels.

Here are the results of that original study:

Based on our qualifications, 71.7 percent of players who enjoyed those spring power surges went on to increased power in the regular season. Moreover, a similar study of that trend on the team level showed similar results.

In recent seasons, we’ve started to see some feedback from independent studies suggesting that trend may no longer hold true. We were curious to investigate, so we ran the same study with the same qualifications on the data from the most recent five seasons, 2009-2013. Here are those results:

What a stark turnaround! For me, the initial study seemed to show a clear trend that indicated spring slugging spikes likely predicted regular season power increases. The same study on recent seasons shows the exact opposite results that, if anything, suggest spring training power spikes indicate a likely decrease in power in the regular season.

In light of the dramatic difference in results between the two samples, I will of course not recommend potential power breakouts based on hitters showing less power this spring. At this point, I’m leaning toward an opinion that the only thing spring stats might predict are which young players may earn playing time.

That said, I can think of reason why the original study and the new study both might have held predictive significance in their times rather than simply showing two small-sample blips that would regress over larger samples. The original study was run from 1996-2001, the height of the steroids era. It was not unusual for players who had never shown power tendencies to suddenly start hitting for power. It stands to reason those changes would show up in spring, following offseasons when players would have had an opportunity to train. Meanwhile, the current study from 2009-2013 is in the presumed post-steroids era, when power across the sport has been on the decline. It will be interesting to continue to track this data in future seasons.