Consecutive Seasons of a Power Decline

You have probably heard of the decline in balls leaving the yard that is present across Major League Baseball. Seemingly all at once we got rid of the PEDs, increased the size of the strike zone, and put all efforts into drafting pitchers that throw 95mph+. As a result, we have been left without many long balls. People everywhere are frantically searching for something new to dig. The trend in fewer home runs has been progressing for the last decade. Looking at the number of home runs hit per season since 1973 (the year baseball implemented the designated hitter in the American league) shows that we are basically back to an early 90s level of power.

As you can see the trend from 2000 on is evident: fewer and fewer home runs. I am not the first person to write about this, nor will I be the last. The game is changing. Power has become a limited resource and teams are certainly willing to pay to acquire it. Look no further than Giancarlo Stanton (avg. 31 home runs per season since 2010) and his $325 million deal for evidence. Stanton demonstrates that this issue is not necessarily affecting everyone. But this made me wonder about players that have seen disappointing declines in the power department over the last few seasons.

To find power-starved players I collected home run data for all non-pitchers that had at least 450 plate appearances in each of the last three seasons. The 450 PA threshold is a mostly arbitrary number but should ensure that we are primarily dealing with every-day players. 81 players met this requirement. With this sample I looked for consecutive declines in the players' HR total of at least 5 HR. Again, 5 is a mostly arbitrary number. I could have used some sort of combination of a drop of 5 one season, and 4 or 3 the next, but decided to keep things simple, and really, a drop of 10 home runs from 2012 to 2014 is fairly substantial. Note that doing things this way excludes any player that hit fewer than 10 home runs in 2012, so there is a better chance that this will catch players that we would consider to have decent power. To account for the fact that players who hit more home runs have further to fall from season to season, I could have used a proportion of the previous seasons home run totals (e.g., 25% fewer home runs); however the proportion selected would be just as arbitrary, and I wanted to keep things simple for this exercise.

In any case, here are the players that met the criteria:

What does this group have in common? For one, other than Billy Butler and Allen Craig these are players who are in their early- or mid-30s and beginning to experience the natural decline that comes with aging. Second, and this should come as no surprise, all of these players experienced considerable changes in their HR/FB rates, which is likely also related to aging. For the most part their flyball rates (FB%) were consistent (Beltre and Craig are exceptions), but the rate at which those flyballs ended up as home runs dropped.

Changes like those shown in the plot are fairly good indications of aging players, or for someone like Allen Craig, the effect of injury. Adam Dunn has elected to retire, so we won't see if his rate would fall any further. But Rios, Craig, and Butler are on the market this offseason as free agents or possible trade pieces. Teams pursuing them will need to take this information into consideration before making a deal. Adrian Beltre still has a year on his deal with the Rangers, and a $16million vesting option for 2016 that requires he accumulate at least 600 PA in 2015. If his power numbers continue to decline, it will be interesting to see if the Rangers give Beltre some extra days off to prevent that option from vesting. Cano is heading into year two of his 10-year deal with the Mariners. It was expected that his offensive numbers would take a hit with the move from hitter-friendly Yankee Stadium to the more pitcher-friendly/neutral Safeco Field, and they did. But he was still worth 5.2 fWAR, so the Mariners are likely not too frustrated with his drop in home runs.

Related to how these players will perform going forward, here is how Steamer projects the 2015 season PA and HR totals for these players:

Steamer projects each of these players to bounce back to be somewhere between their 2012 and 2014 totals. Evidently, not completely buying the downward trend just yet; good news for their respective teams.

Generally, it remains to be seen how the trend in declining home run totals will continue. It could just be part of the natural cycle that the game moves through over time, or perhaps the powers that be will do something to effect change. Implement the designated hitter in the National League? Enforce a pitch-clock to speed up the game, possibly affecting pitchers' control/command? Have umpires call a smaller strike zone? These are all possibilities, but knock-on effects of any implementation could have us discussing different ‘problems' in years to come. We will have to wait and see how the home run numbers end up in 2015 and over the next few seasons. Regardless, teams are taking note of the downward trend in power numbers and will work to build their rosters accordingly.

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All statistics courtesy of FanGraphs and Baseball-Reference.

Chris Teeter is a featured writer and editor at Beyond the Box Score. You can follow him on Twitter at @c_mcgeets.