The Mariners Have Been Very Average This Year

This issue got brought up at Seattle Sports Insider with M's Tilt at Pythag Windmill. They seem to be winning more games than their runs scored and runs allowed would normally indicate. Here are the comments I made about the issue:

"Maybe the Mariners are not so bad. Here is what their hitters have done:

OBP .313
SLG .400
OPS .713

Here is what their pitchers have allowed

OBP .312
SLG .395
OPS .712"

And

"The Mariners have allowed 63 unearned runs this year. The league average is 50.

A quick regression shows that runs per game in the AL this year is

R/G = -5.69 + 21.03*OBP + 8.04*SLG

That predicts them to score about 4.11 per game while it is actually 3.95. Over 148 games, it amounts to 24 runs below expectations. So now we have already accounted for 37 of their -53 run differential (584-637).

Now for runs allowed the equation is

R/G =-4.14 + 22.78*OBP + 3*SLG

(maybe fielding and relief pitching are the reasons this is different than the hitting formula-I really don't know-could be small sample or one year of data)

That says they should allow 4.266 per game and it is really 4.304. Over the 148 games it adds up to 5.59 runs. So now we are up to explaining over 42 of the -53 runs in their differential (which should be very close to zero given their stats I mentioned above).

So I think they have been a little unlucky hitting wise, scoring 24 fewer runs than expected. Then they are allowing too many unearned runs. Also, if I applied the hitting formual to their pitching stats, it would mean they have given up 26 more runs than expected. That could be bad luck or a weak bullpen. My guess is that they know about all this."