Another one of Bill James' newfangled number thingies.  Here's David Appelman's simple, non-numbers description:

We’re using the 4 component version, which is an average of Stolen Base Percentage, Frequency of Stolen Base Attempts, Percentage of Triples, and Runs Scored Percentage.

For the hardcore number geeks, here's David's description of the formula in the same thread:

Stole Base Percentage = (((SB + 3)/(SB + CS + 7)) - .4) x 20

Frequency of Attempts = Square root of ((SB + CS)/(1B + BB)) / .07

Percentage of Triples = 3B/(AB-HR-SO) and then put on a scale based on this chart:

< .001 = 0
.001 - .00231 = 1
.00231 - .00392 = 2
.00392 - .00583 = 3
.00583 - .00804 = 4
.00804 - .01055 = 5
.01055 - .0136 = 6
.0136 - .01587 = 7
.01587 - .01898 = 8
.01898 - .02239 = 9
> .02239 = 10

Runs Scored Percentage = (((R - HR)/(H + BB - HR)) - .1) / .04

Then anything one of the components that is below 0 you make 0, anything about 10 you make 10. Then take the mean of the 4 components.

As for how good or bad a Speed Scale is:

The scale is 0-10, The higher the better. Average is around 5.

Now, I don't know if this is a very useful stat in terms of predictive value, but it's pretty cool nonetheless.

Top 5 Speed players so far this year:

Carl Crawford--8.9

Michael Bourn--7.7

Coco Crisp--7.6

Matt Kenp--7.4

Chone Figgins--7.1

Pretty much your usual suspects there.

As for the top 5 leadfoots in the league:

Ramon Hernandez--0.6

Dan Uggla--0.6

Mike Jacobs--0.6

J.J. Hardy--0.6

Pat Burrell--0.6

At first I was a bit surprised to see Hardy at the bottom, as I've always assumed he was at least competent on the basepaths, but the numbers proved me wrong; he is 5-for-5 on stolen bases.  In his career.  In four years.  There goes my theory that guys who play SS well (and he is very solid at SS; career 11.9 UZR/150) have good baserunning speed.

So what about the Mariners?

As a team, the M's are a 4.1 at Speed.  This ranks them 26th in the league, and 12th (out of 14) in the AL.  This probably isn't too surprising, as aside from Ichiro, Beltre and maybe Endy, we don't exactly have a group of hellions on the basepaths.

The bottom Speed guys among M's players is rather predictable:  Jamie Burke at 0.1, and Sweeney and Griffey at 1.3 both.

As for our top Speed guys, the top 4 goes, uh, mostly predictable:

Ronny Cedeno:  4.1 (PETR!)

Adrian Beltre:  4.3 (his inexplicable decision to steal third earlier tonight will probably affect this rating)

Ichiro!:  4.7

And our number one Speed player, is......

Rob Johnson?

Rob motherfucking Johnson?

Rob MotherFuckingCockSucking Johnson has a 5.0 Speed Score?

No wonder Wak continues to keep him on the major league roster while Clement rots in Tacoma.  Rob Johnson is a speed demon, who strikes fear into the hearts of opponents with his baserunning prowess, whose clubhouse grit would make Griffey say, "yeah, he's the leader here."

Rob Johnson:  your basepath demon.

Ladies and Gentleman, your 2009 Seattle Mariners!