The following three players have been: (1) Junior's natural :- ) comps since about 1992, and (2) guys who were verrrrrrry capable of playing baseball at age 39.

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Frank Robinson played 50 games, just over 100+ AB's, and had one of his best lines in this tiny amount of play: .237/.385/.508 with a 153 OPS+ and a 2:1 eye (in 1975). 1975 was my favorite baseball year as a boy, but I don't remember whether Robbie was hurt or what. Here is the '75 Indians team, which had the DH. Two good OF's, a great DH, and one mediocre developmental OF in front of Robbie.

Robinson's eye ratio strongly indicates that he'd have hit very well in full-time play.

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The Say Hey Kid hit .291/.390/.506 with a 139 OPS+ at age 39 -- in full-time play. He was 8th in the NL in offensive winning percentage, a Bill James stat.

At 40, Willie led the entire NL in OBP at .425 and drew votes for MVP. He started in CF for the All-Star team both seasons. He was not using steroids.

At 41, Willie was also an excellent player in part-time action. At 42 he was a painful sight (that I remember very well). But at 39-40, he was probably at least as good a player as (say) Adam Dunn is right now.

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Interestingly, b-ref.com's formula does not list Henry Aaron as a comp for Griffey, despite Hammerin' Hank being one of Griffey's three most natural comps.

At 39, and this being 1973, Hammerin' Hank put up a stunning .301/.402/.643 line for a 177 OPS+. The next year, at 40, he had a 128 OPS+ and then at 41 and 42 was mediocre though competitive.

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Just for fun, you might remember more recently that Edgar Martinez was terrific at 39 and also at age 40, posting .400+ OBP's and near-.500 SLG's in Safeco.

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=== A Handful of Comps, Dept. ===

Robbie, Aaron and Mays, along with Junior, were:

1. Super-coordinated

2. *Freakishly* -talented

3. Black men

4. Playing CF (Robbie and Aaron played it when young; anyway, all were go-get-'em OF's)

5. With moderate builds (generally these guys were 5'11", 180 lbs or so)

When Griffey was still in his 20's, Bill James predicted that Griffey would have problems running when in his 30's: "I don't know if you've ever noticed this, but Griffey has big, heavy thighs. He certainly runs well now, but I doubt he will at 35." Griffey differs from Aaron, Mays, and Robbie by virtue of the fact that Junior is a noticeably bigger man.

The natural Barry Bonds would have gone in this list, and would have been more Griffey's physical size.  He would be the 4th player in the 5-man group and also would probably have been a star at 39.

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=== Dr's Diagnosis Dept. ===

I'll frankly admit that I was surprised by what the comps indicated. I thought that by the time you got to 38 and 39, you'd be talking about guys hanging on -- some 105's, some 123's maybe, but the real electricity certainly gone by age 39.

Instead we found:

153 - Robbie's OPS+ in part-time play (per eye ratio, he could have been a star in 450 AB's)

139 - Willie Mays' OPS+, and was an MVP candidate also at 40

177 - Aaron's OPS+, and was 128 the next year at 40

999 - Bonds' OPS+ ... presumably he'd have been at least "very good" as a natural player

140* - Edgar's at 39 and 40

The fact is, that I sat down to write this article with the expectation of writing that at age 39, Griffey's magical seasons were over.  I suddenly realized that they aren't, necessarily.

I'm still not telling anybody to expect a big season from him.

But it is interesting that -- ignoring the specifics on Griffey's splits and injuries -- strictly from the standpoint of general age barriers for "Naturals" like him -- Junior could be one of the best hitters in baseball at 39, and the Mariners' best hitter at 40.

Cheers,

jemanji