Is Barry Bonds really the home run king?

Barry Bonds is seemingly cruising to and past Hank Aaron’s home run record. At the start of the season there was some doubt as to whether he would achieve the magic number in 2007, but a slew of long balls in April and May ensured that he will (barring catastrophic injury). In fact, with the way he is swinging the bat there is a fair chance that Bonds will continue playing in 2008 and possibly, heaven forbid, beyond (watch out Julio Franco).

However, it might all have been so different. And no, I’m not talking about the steroids fug, but rather about whether Bonds would still be aiming for the same high-water mark or one that was more lofty set by Ken Griffey Jr.

Let’s investigate some more.

The early days of Junior’s career

Junior has had a career of two halves, roughly defined by his switching teams from the Mariners to the Reds in 2000. Take a look at his stats since he burst on the scene in 1989, his rookie year (that’s not a typo—he has been in this business for 19 years):

Year    Ag      Tm      G       AB      HR      HR/AB
1989    19      SEA     127     455     16      3.5%
1990    20      SEA     155     597     22      3.7%
1991    21      SEA     154     548     22      4.0%
1992    22      SEA     142     565     27      4.8%
1993    23      SEA     156     582     45      7.7%
1994    24      SEA     111     433     40      9.2%
1995    25      SEA     72      260     17      6.5%
1996    26      SEA     140     545     49      9.0%
1997    27      SEA     157     608     56      9.2%
1998    28      SEA     161     633     56      8.8%
1999    29      SEA     160     606     48      7.9%
2000    30      CIN     145     520     40      7.7%
2001    31      CIN     111     364     22      6.0%
2002    32      CIN     70      197     8       4.1%
2003    33      CIN     53      166     13      7.8%
2004    34      CIN     83      300     20      6.7%
2005    35      CIN     128     491     35      7.1%
2006    36      CIN     109     428     27      6.3%
2007    37      CIN     83      294     23      7.8%

Back in his formative years his home run rate climbed from 4% to a peak of around 9% as he started to slam 50 fence-hoppers a season. By the time he had left the Mariners to move to the Midwest he had already amassed 398 home runs and seemed destined for an assault on Hank Aaron’s mark of 755. All that was required of him was to stay healthy and motivated. (Note: At that point Bonds had ratcheted up 445 homers although he had been playing for three years longer—like for like over the same time period Bonds recorded 380 longballs.)

Griffey and Cincinnati

Unfortunately, as all know, Griffey’s career in Cincinnati has been anything but healthy. In Seattle he racked up seven seasons where he played in at least 150 games (it may have been more were it not for the 1994 strike). He is currently in his eighth season in Ohio and only in one year, his first, has he come even remotely close to that total.

Every season between 2001 and 2006 the DL seemed to be Griffey’s second home. In total he hit the doctor’s surgery an eye-watering eight times in those six years, missing a total of 274 games—we’re not just talking about a sniffle here; that is some serious time out. For the sadists among you here is the gruesome run-down:

2001: Once, hamstring tear
2002: Twice, torn knee tendon and that darn hamstring again
2003: Twice, dislocated shoulder and torn ankle tendon
2004: Twice, yup, those hamstrings again (x2)
2005: None,but had a foot injury when on the 40-man roster (so wasn't on DL)
2006: Once,inflamed biceps tendon (right knee)

Unbelievably he also broke his wrist in the 2006 offseason wrestling with his kids but managed to recover in time to start mashing the ball again in 2007—you couldn’t make this stuff up.

It isn’t only injury that may have prevented Junior from notching some gaudy home run numbers later in his career. Fans and the media have also questioned his motivation while wearing the stripes of Cincinnati. First there was the hullabaloo over his jersey number. He initially wanted number 24, which he wore in Seattle, but it was already retired in honor of Tony Perez. That meant he had to settle for number 30, his Pop’s old number, but he sure kicked up a helluva stink in the process.

Further there were suggestions that Griffey was too focused on exploring other non-baseball commercial opportunities and did not pay enough attention to his fitness in his late 20s, which may have prevented some of his more serious injuries. For instance, in the late ’90s and early ’00s he appeared in a number of baseball games, an episode of the Simpsons, The Fresh Prince of Bel Air, and baseball movies Little Big League and Summer Catch. Another theory is that the turf of the Kingdome wreaked havoc on his legs in his later years.

All of this is incidental to the central question: Had he stayed healthy would he have established a new home run record?

The short answer and the long answer

Let’s start with the short answer so you can click on to the next article! Griffey has missed about 300 games due to injury since his time in Cincinnati. Doing the math on the games he did play he hit a home run a little over once every four games, on average. That equates to an additional 75 home runs, which moves his total to 660.

However, that also includes a couple of seasons where injury clearly took the edge off his performance (2002 and 2003, for instance). Normal seasons in those years may have yielded another 20 long balls boosting his total to about 680. That would put him about 80 shy of Aaron and Bonds—still some gap. He would need to play for another three to four years in order to snatch the record, which would by no means be a certainty; it also presupposes that Bonds will hang up his spikes sooner rather than later.

Okay, that quick and dirty exercise assumed that Griffey maintained his historic production, but perhaps injury hampered his assault on the record more than we think. Let’s turn our attention to the long answer and try to be marginally more scientific about the whole process. Given that he completed his tour in Seattle largely unharmed it isn’t too unreasonable to assume that he was following a fairly typical aging profile (as far as age curves are typical).

Here is a typical home run aging curve, courtesy of Tangotiger:

Age     Home run factor*
21      0.68
22      0.78
23      0.88
24      0.91
25      0.95
26      0.98
27      1
28      0.99
29      0.98
30      0.96
31      0.95
32      0.92
33      0.87
34      0.86
35      0.8
36      0.76
37      0.71
* A value of 1 indicates peak age; all other numbers relative to this

This curve has been calculated using a match pairs process. This involves looking at players in consecutive years, comparing home run rates and weighting by the lowest PA in the two years. Rinse and repeat for every player above a certain plate appearance cut-off and you get the data above.

A value of 1.00 represents peak age, and for home runs that occurs at age 27. From that point on you can see that home run skill gradually drops off. If we apply the age curve backwards to the first part of Griffey’s career we see that between the age of 22 and 28 he hit 290 home runs against 350 predicted (assuming 150 games a season), though that includes a season out (parts of 1994 and 1995), which accounts for a lot of the gap.

Let’s apply Tango’s aging curve to Griffey after the age of 28 and see how many home runs he should have hit from the point he joined Cincinnati (again assuming 150 games a season). To get the baseline home run I’ve averaged his 26-28 years of home runs in Seattle and applied the aging curve from that point.

Age         Actual HR   Adjusted HR    Age factor
29          48          53             0.98
30          40          52             0.96
31          22          52             0.95
32          8           50             0.92
33          13          47             0.87
34          20          47             0.86
35          35          44             0.8
36          27          41             0.76

Age 19-28   398
Age 29-36   333
This season 21
TOTAL       752

Wow! 752—although the assumptions are a tad aggressive perhaps (including his age 27 and 28 seasons gives him more than six 50-home run seasons)! Remember that this analysis does not include 2007, so if you add Junior’s 21 longballs this year then it is he and not Bonds who would have smashed the record. Add in the fact that Bonds is a few years older and there would be no debate as to who was the best slugger. Or would there be?

Bonds fights back

One thing that is worth noting is that Griffey has played most of career in hitter-friendly confines, whereas Bonds, for the last decade or so, has been fighting sea breezes blowing in from San Francisco Bay. We can partly adjust for this by applying a park factor. I have chosen Baseball Reference’s park factor for simplicity. This is a batter park factor rather than a home run park factor and won’t be pure (as Griffey’s and Bonds’ hitting are included in the calculation). Anyway, with those limitations in mind take a look at what the park factor does to the home run totals (note: the home runs are based on actual totals and not on the above age-adjusted numbers):

Ken Griffey Junior                        Barry Bonds
Year    Team    HR     PF      Adj. HR    Year    Team    HR    PF      Adj. HR
1989    SEA     16     103     16         1986    PIT     16    102     16
1990    SEA     22     101     22         1987    PIT     25    101     25
1991    SEA     22     100     22         1988    PIT     24    99      24
1992    SEA     27     101     27         1989    PIT     19    97      20
1993    SEA     45     100     45         1990    PIT     33    96      34
1994    SEA     40     102     39         1991    PIT     25    98      26
1995    SEA     17     103     17         1992    PIT     34    99      34
1996    SEA     49     100     49         1993    SFG     46    96      48
1997    SEA     56     99      57         1994    SFG     37    95      39
1998    SEA     56     100     56         1995    SFG     33    96      34
1999    SEA     48     103     47         1996    SFG     42    96      44
2000    CIN     40     107     37         1997    SFG     40    98      41
2001    CIN     22     99      22         1998    SFG     37    96      39
2002    CIN     8      108     7          1999    SFG     34    89      38
2003    CIN     13     100     13         2000    SFG     49    91      54
2004    CIN     20     92      22         2001    SFG     73    91      80
2005    CIN     35     106     33         2002    SFG     46    91      51
2006    CIN     27     108     25         2003    SFG     45    99      45
2007    CIN     23     108     21         2004    SFG     45    103     44
                                          2005    SFG     5     98      5
                                          2006    SFG     26    100     26
                                          2007    SFG     17    100     17

                       TOTAL   576                              TOTAL   783

That chart illustrates just how good Bonds was and is. Not only has he hit over 750 home runs, but he has done it in a park that by all accounts is a pitcher’s haven (God bless Barry Zito). Based on the Baseball Reference calculation, Bonds’ park-adjusted home run figure is 783—he would have passed Aaron last year.

Final Thoughts

The home run record is all about one man at the moment: Barry Bonds, although Alex Rodriguez could enter the picture at some point in the future. However, had Junior remained healthy we could have been in the process of witnessing a historic two-horse race and the spectre of steroids would have made Griffey the firm fan’s favorite.

As it is Griffey will join the 600 club soon and will be an automatic Hall of Famer. A great career for sure, but at the turn of the century it promised to be perhaps the greatest ever.

References & Resources
Baseball Reference remains an invaluable source for all things baseball (and probably a lot of things non-baseball)!

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