Breaking Balls

Okay, it looks like I gotta publish something to avoid becoming the Steve Trachsel of the blog world. I had a big fancy post planned to rant about game durations and look at some factors that play into them. I was actually planning to discuss the ridiculous slowness of Red Sox games (and how much Sox-Yanks games alone may have skewed BP's study of game durations and fielding performance), until the team itself scooped me by playing a high profile "slug" fest on Friday night. I guess that's what I get for snoozing on the job.

Instead, I'll talk about another trend that bears watching. The home run is possibly the one statistic we understand best in baseball. It is not reliant on external factors such as fielding, and it only indirectly depends on the umpire's strike zone. The home run is beautiful because it is the only single event that purely encapsulates the duel between pitcher and batter (ok, the ballpark and game conditions have some say, as well). Any pitch can be clobbered out of the park, and every batter prefers that his plate appearance end in this way.

This year, however, chicks who dig the long ball have quietly started following a different sport (NB: those values are in yards). This season has been marked by a significant dip in home runs, as many of the consistently premier sluggers of the past have experienced power outages to varying degrees. It is my opinion that a drop in an individual's performance from year to year can be indicative of any of a number of causes. Sometimes a performance at the very top of a guy's capabilities is followed by a sharp regression to the mean, or the age curve hits like an age cliff. Other times there are more sinister forces at work. Regardless, I feel safest publicly treating year-to-year fluctuation in a hitter's output by awarding the benefit of the doubt to the athlete.

Fluctuations in power numbers across the league, however, call for further scrutiny. How is it that, after seeing 34 players hit 30+ HR last year, only 25 are on pace to meet that milestone this September? Even more dramatically, only seven hitters are on pace to hit 35+ HR this year, while 23 did so in 2006. The 40 HR club has been trimmed from 11 in '06 to a mere 5 a year later. I'm going to come at this question from a few different directions, and we'll see what we get.

My first approach is to look at the home run rankings of the last two years as simple lists of numbers, each tied only to its place in the hierarchy of HR totals. By eliminating the names associated with each line, we avoid the temptation of comparing David Ortiz's monstrous 2006 total (54 HR) to his merely excellent 2007 (34* HR - all projected 2007 numbers will be notated "*"). Instead, I contrast his second place total from 2006 with Prince Fielder's projected total of 2007 (50* HR), a mere 7.5% drop, rather than a 37% decline. This is more representative of the levels of play across the two seasons; understandably, players past their primes (like Ortiz) have declined, and younger players (like Fielder) have blossomed as they follow their expected age curves.

I should probably acknowledge here that a more perfect study would use HR rate in place of the counting stat, but I couldn't figure out a way to get Marcus Thames out of the top ten without doing something dishonest. Even though he and Tony Clark could hang out, leaving them there would fail the "Does it make sense?" test. Without further ado:

        2007        2006
#    HR*   PA*    HR   PA   Percent change
1    57    711    58   704   -2.54%
2    50    677    54   686   -7.40%
3    43    609    49   634  -11.27%
4    42    662    46   728   -7.84%
5    41    638    45   646   -8.21%
6    35    713    44   611  -20.95%
7    35    678    42   564  -17.18%
8    34    694    42   610  -19.77%
9    34    673    41   617  -17.81%
10   33    699    41   669  -20.46%
11   33    672    40   683  -18.48%
12   33    671    39   559  -16.38%
13   33    662    38   618  -14.18%
14   33    625    38   634  -14.18%
15   33    470    38   660  -14.18%
16   32    726    37   579  -14.80%
17   32    712    37   695  -14.80%
18   32    699    35   558   -9.93%
19   32    645    35   608   -9.93%
20   32    623    35   643   -9.93%
21   30    701    35   672  -13.04%
22   30    651    35   674  -13.04%
23   30    595    35   689  -13.04%
24   30    538    34   661  -10.48%
25   30    515    34   663  -10.48%
26   29    778    34   667  -13.68%
27   29    691    33   665  -11.06%
28   29    616    33   699  -11.06%
29   28    707    33   727  -14.36%
30   28    594    32   557  -11.68%
31   28    562    32   677  -11.68%
32   27    571    32   739  -15.08%
33   27    592    31   611  -12.34%
34   27    603    30   586   -9.42%
T: 1130* 21972* 1297 21993  -12.96%

As you can see, the top 34 sluggers in the land are projected to finish with almost 13% fewer total home runs than their predecessors of 2006, in almost exactly the same number of plate appearances. Why is this? Are the younger players not rising as quickly as the older guys fall? Was the 30+ dinger class of 2006 particularly heavy on aging stars?

It bears noting that this year's top 34 power group includes breakouts Miguel Cabrera (projected to reach +34.6% over his 2006 HR total), Hanley Ramirez (+76%), Prince Fielder (+78.5%), Brandon Phillips (+88%), Ryan Braun (0 to 33*...yep, that's infinity), Chris B. Young (from 2 HR in '06 to 33* this year) and Carlos Peña (+4,200%). That means that last year's group must have crashed and burned even harder than a first glance reveals. A closer look confirms this thought, as 18 of the 34 HR leaders of 2006 have dropped out of that bracket this season, meaning none is on track even to break the modest 27 HR mark in 2007. This plummet from the upper tier becomes even clearer when we consider that this season actually had more hitters that reached the 20 HR mark than yesteryear. The 30+ HR hotshots of '06 sank into the second tier, while they were replaced in the (slightly lowered) first tier by a new batch of boppers.

In the next few days I will expand this study to look at three different outcomes the stars of yesterday found in 2007, as well as league rates and the grand scheme of things.