Posted by Andy on April 27, 2011
I was just perusing the 2011 MLB baserunning splits and did a sort by XBT%, which is the percentage of time that a baserunner advances more than 1 base on a single or more than 2 bases on a double.
The league average so far this year is 41% but check out the teams with the lowest percentage so far:
The Yankees have by far the lowest percentage. It's an unusually low number as in most seasons the best and worst teams don't usually vary from the average by more than 6 or 7 percentage points.
Initially, you might think that the Yankees' low percentage indicates that they're having trouble scoring runs, but they're not. (Check out the first column above.)
In truth, what's happening is that the Yankees are homering a lot when the guys are on base, and as a result they don't actually have all that many baserunning situations. Note how many fewer situations they have in the columns to the right above, and it turns out that with such a small sample size, they just happen to have had some bad luck so far.
How much does it normally correlate with run scoring in normal cases? Not a ton. I took a look at the 2010 numbers, and there's quite a weak correlation between XBT% and R/G. For those who care, I found just a 0.10 R-squared on a linear correlation.