Situational in Seattle

Are the Mariners scoring more runs than they should be?

The Seattle Mariners have jumped out of the gate, and are solidly in control of the AL West, if not all of baseball.  Despite reduced scoring this year, their offense is clicking; an average of more than 6 Mariners cross the plate each game, 25% more than the league rate!  Is it for real, or is it simply a fa?ade of timely hitting and lucky bounces?

Using sabermetric tools, we can closely examine the workings of the Seattle offense. Early research by Bill James has shown that teams tend to regress towards their predicted runs total, rather than maintain large discrepancies from it.  A prediction of runs scored can be made using eXtrapolated Runs (xRuns) .

TEAM           RUNS       BA      OBP      SLG     xRuns
Seattle         460    0.284    0.360    0.447    438

We can see that the Mariners are over-performing by about 22 runs.  That’s not a huge figure, but it is significant: about 2 wins.  How did the Mariners score those 22 runs?  A few years ago, in a drastic departure from normal sabermetric standards, Bill James started using situational statistics in his runs created estimations. 

Although the adjustments for batting with runners in scoring position and home runs with runners on base increased the accuracy of his estimations, it reduced the independent nature that aids analysis and increases predictability.  Much like teams regress towards their predicted runs scored over the course of a season or group of seasons, situational statistics do not demonstrate consistency.  A team that is batting .250 overall, but .300 with the bases loaded in June, is more likely to finish the year batting .250 in both situations than to maintain its statistical split.

However, we can use his adjustments to help us see why the Mariners are scoring those extra runs.  The first adjustment is for batting average with runners in scoring position (RISP).  James reasoned that each extra hit in that situation was worth an extra run, thus by comparing regular batting average and batting average with RISP, the extra value of those hits can be counted. 

The Mariners have batted .284 overall this year, and have come to the plate 760 times with RISP.  We expect that they would have 216 hits in that collection of at bats; the Mariners actually have 234 hits with RISP.  James adjustment explains a large part of the discrepancy by adding 18 runs to Seattle’s total.

The second adjustment is for home runs with runners on base.  James reasoned that an extra homer in that situation was worth an extra run, so by comparing home run rates overall with rates with runners on, we can see how many runs that type of situational hitting added.  Seattle has hit 0.03 homers per at bat and batted 1241 times with runners on.  We would expect that they would hit 40 homers in those 1241 at bats.  They have hit 42.  We can add 2 more runs to their situational tally.

Simply by examining two situational statistics and applying crude adjustments, we can see the mechanism that the Mariners’ offense has used as it overachieves: they have had timely hitting.

Team          Runs    xRuns    Difference    Situational Runs
Seattle        460      438            22                  20

Some would argue that the Mariners possess a talent for situational hitting.  It’s possible, but so is spontaneous human combustion.  As Voros has written before, a lot can happen in a small sample size - and on a team scale, the number of at bats with RISP is a small sample.  I would expect them to relapse a bit and drop closer to their predicted xRuns.  It’s important to note that even with the 22 run penalty (or rather, without their 22 run situational bonus) the Mariners would still be 15 runs ahead of second place Cleveland’s 423 runs total.

The Mariners’ offence is for real - but, that doesn’t mean they haven’t been lucky!

How long do to you expect this to last?

Batting Average       Overall    RISP
Ichiro                   .383    .500    (31 for 62)

Situational statistics are valuable as a tool to explain events that have already happened; however, the do not track ability and have little predicative value.  In this case, we can see why the Mariners have performed as well as they have; however, I do not agree with this type of adjustment for estimating runs. 

For a method as well publicized as James’ Runs Created, the introduction of situational statistics is silly.  Runs Created is meant to track what should have happened if all the bounces evened out, and thus has more value in predicting what will happen.  If James wants to analyze what did happen and look at the differences from the expected, he should use a more comprehensive analysis of situational statistics such as Value Added Runs.  He has the data, we don’t.  Luckily, we can still analyze the situations using the James methods.