=== Previously on SSI, Dept. ===

BaseballHQ wanted a set of stats that "correlated well" with actual, physical home-to-first footspeed.  In other words, they wanted to be able to tell who the track guys were, and they wanted to use only stats to find that out.

So they took a 400-player list of home-to-1B times (3.9 to 4.5) and put a Bunsen Burner under the stats until they found just the right four stats.

It turned out that Bill James' ancient Speed Score had done just as good a job as HQ's new SPD metric.  But Bill's Speed Score relied heavily on stolen bases ... HQ wanted to know which guys had the potential to steal bases.

James' old Speed Score used:

• SB attempt rate
  
• SB success rate
• 3B's per ball in play
• Runs scored per time on base

HQ's new SPD uses:

• R - HR / RBI - HR
• 3B / 2B + 3B
• GB hits / GB (counting only soft and medium GB's)
• Body Mass Index (less weight, per height, is better)

Both scores wind up with about an 0.75 correlation to footspeed down the line out of the batter's box.  I assume that Franklin Gutierrez is one of the 0.25, since he has the home-to-1B time of Bill the Beerman, but is a little over 100 on SPD.

::crinkledpapercups::

No, actually, we don't want to make Franklin out to be doing a Godzilla Stomp around the field out there.  He's consistently 105-110, peaked at a very respectable 118, and even that is probably affected by the fact that his swing prevents him from getting a good jump out of the batter's box (GB hits / GB).

Franklin runs well.  It's just that Denard Span and Curtis Granderson run better than well ;- )

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=== Various and Sundry ===

One interesting idea we hadn't yet mentioned:  the Bill James Speed Score age-arc is quite a bit different than the HQ SPD arc.

In other words, if you're just asking how fast a player runs, the answer is:  he's at his fastest at age 23, and then he declines rather subtly the rest of his life.

If you're asking how much a player's speed helps him on the basepaths, the answer is:  he's at his fastest at age 28, and then he falls off real quick from there.

It's interesting; James' Speed Score measures an intersection of footspeed and experience.  HQ's new and valuable SPD metric measures footspeed more purely.

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