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June 4, 2014

Pebble Hunting

The Baseball Bloodlines Project

by Sam Miller

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A word you’re going to hear during this week's draft is “bloodlines.” Nick Gordon will get drafted early in the first round, and noted will be his bloodlines—son of Tom, brother of Dee. Cobi Johnson will get drafted in the supplemental round, and noted will be his bloodlines—son of Dane, who you’ve never heard of, but still, bloodlines. If last year is a good guide, around 100 of the 1,200 players drafted will have been sired by pro ballplayers. (Many others will be brothers or nephews of pro ballplayers.)

That’s one way of doing the math. I wondered about the other way of doing the math: If you start with a ballplayer and make him mate, what are the chances his offspring will be drafted? I’ll warn you right now that the front end of this research took much longer than I anticipated, the result being that I’ve got a couple things to say that you can read in about 15 seconds, and then the article will be over. You’re warned.

I went back to 1978. I pulled up all of the major leaguers who appeared that season. I wanted something close to a random sample of them, so I sorted by plate appearances and selected every fifth name. Then I tried to find their kids.

This isn’t always easy. Bobby Bonds’ kid was easy to find. Dave Winfield’s kid was easy to find. Bruce Kison’s kid was easy to find. But then you get to Tony Scott, a guy who produced 3.3 WARP in his career and is named Tony Scott, and before you know it you’ve spent 20 minutes on genealogy web sites and all you’ve learned is that your great, great grandfather’s surname means “master of horses” in Gaelic.

So this is an honest, but non-rigorous, attempt at answering this question, but if you spot a mistake let me know!

I investigated 118 players. Ivan De Jesus was the first. His son was drafted. Craig Skok was the last. His son was not drafted. Some of these players didn’t have sons, or children of any kind, but they’re all counted. Put together, we have this:

  • Total players: 118
  • At least one son drafted: 27

It’s more likely that I missed some than that I made some up, so if anything that second number might be higher. So: If you’re a major-league ballplayer, you have about a one-in-four chance of producing a son who becomes a pro ballplayer. About half as likely as my chances of producing a son.

There are multiple factors going on here, of course. One is that pro ballplayers’ bloodlines are valuable bloodlines. Pro ballplayers tend to have pro baseball bodies, so their kids, do, too. They tend to have pro ballplayer baseball expertise, which they can pass on to their kids. We might presume they’re usually men of means, who can pay for travel-ball expenses and the nicest pitchback machines. On merit, they will produce more pro ballplayers.

Also, their kids benefit from the occasional nepotism pick. They might also benefit from the expectation of a bloodline effect—Robbie Kison might get more looks than Robbie Notkison would with similar skills, tools, and physical characteristics.

Here are our 27, categorized in categories:

The major leaguers:

  • Ivan De Jesus Jr, second round, 80 plate appearances
  • Barry Bonds, first round, 12,606 plate appearances
  • Jose Cruz Jr, first round, 5,448 plate appearances
  • John Mayberry Jr, first round, 1,290 plate appearances
  • Gary Matthews Jr, 13th round, 4,617 plate apearances
  • Keith Kessinger, 36th round, 32 plate appearances
  • Dusty Wathan, undrafted, six plate appearances
  • Lance Niekro, seventh round, 535 plate appearances
  • Josh Roenicke, 10th round, 220 innings pitched

The high picks or high minors

The low picks/low minors

The non-signers/didn’t play

We can rule out nepotism for the first group. While the favor-to-the-friend draft picks are a quirk of the game, the league is fairly meritocratic (or at least tries to be), and any player who worked his way up to the majors was a player.

I think we can probably rule out nepotism for the second group. Those guys were all either taken with picks too valuable to throw away, or they proved their skills by advancing up the ladder; even if one was a nepotism pick, he did enough as a ballplayer to assume he’d have gotten a chance somewhere down the line.

The bulk of the third and fourth groups probably wouldn’t have been drafted if they had less familiar names, I think. Not all of them; I don’t want to cast aspersions on any one of these fine young men. But the bulk of them, probably.

So readjusting our predictions: We started with 118 major leaguers, and we ended up with nine big leaguers, and an additional seven legitimate draft picks or minor-league careers. One in 13 major-league ballplayers sired a major-league ballplayer. Those 118 major leaguers produced nearly 200 WARP of offspring, though the bulk of that came from one man, and if Bobby Bonds hadn’t fallen on a multiple of five when I sorted it would be a very different figure. So don’t take that number seriously at all.

One “pattern” that emerged while I was doing this was that the further down the list I went—the list being sorted by plate appearances, a marginal proxy for player quality—the scarcer these sons became. The full-time position players, the guys getting 600-plus plate appearances, produced a nearly 40 percent rate of draftees. Ben Lindbergh and I once wondered about this on Effectively Wild: Do the effects of bloodlines get stronger based on the quality of dad, or do a Low-A washout and a Hall of Fame big leaguer pass on the same (more or less) genetic advantages to their children? I guessed that they did, that the difference between Tony Gwynn and Chris Gwynn is irrelevant at a genetic level.

I started to second-guess my hunch while going down the list, though, and seeing the hit rate taper off. If better big leaguers are more likely to produce big leaguers, then the very best big leaguers should produce the very most big leaguers. So I ran down the greatest players ever, the 38 players (including pitchers) in history who produced 85 or more WAR (excepting the couple whose kids are too young to evaluate).

To the best of my knowledge, these are the descendants of those 38:



Totals: 38 players, 50 sons. Thirteen were drafted or played pro ball, but only one made the majors, for a total of 299 plate appearances.

We get a similar rate of pro appearances, but far fewer made the majors. This concludes nothing, which is maybe its own sort of conclusion. I have nowhere else to take this, or at least nowhere to take it in the time I have to file this article to the internet. It would certainly be interesting to compare every bloodline pick with the expected career for his draft position. Are bloodline picks overvalued or undervalued? That’d be an interesting thing to look at. Heck, get enough of these and it’d be interesting just to see what the average son of a big leaguer produces in the majors—I’d guess, if I were guessing, that the son of a major leaguer is likely to produce, on average, about a half a win just by being born. Maybe another day we’ll do that. For now, you know some things.

The SABR bio project was extremely helpful in collecting this information. For simplicity, “drafted” was used interchangeably with “played pro ball” for sons in pre-draft generations.

Sam Miller is an author of Baseball Prospectus. 
Click here to see Sam's other articles. You can contact Sam by clicking here

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