# 4/22/13 – What are the Errors Costing the Cubs?

If you have watched the Cubs at all this past week, you wouldn’t have to watch long to see some pretty sloppy defense. As of today, April 22, the Cubs have committed 17 errors in 17 games, resulting in a league-leading 14 unearned runs. In fact, 18.9% of the runs scores against the Cubs this year have been unearned. Only the Washington Nationals have committed more errors so far this season with 18. This got me wondering if there was a way to quantify or estimate how many wins the Cubs lost due to these unearned runs. I decided to use Pythagorean expectation to try and quantify wins that were lost.

First, if you need it, here is a little background about Pythagorean expectation. Bill James was the inventor of the original formula used to predict winning percentage, which was

Recently, Baseball Reference, changed the exponent to 1.83 to make the formula more accurate. So, I am using the Baseball Reference formula

Currently, the Cubs’ record is 5-12. Using Pythagorean expectancy, 57 runs scored, and 74 runs allowed, their Pythagorean record is 7-10. Without even talking about earned runs, this already tells us that the Cubs should have a better record than they do, given the runs the have scored and allowed. Now, if we take away the 14 unearned runs the Cubs allowed, their Pythagorean record is 8-9, nearly 0.500. So, the 14 unearned runs have hypothetically cost the Cubs 3 wins.  Another way to think about this, each unearned run has costs the Cubs 0.21 wins.

An important thing to remember with all of this is that it is totally hypothetical. Last year, the Cubs’ final record was 61-101, but their Pythagorean record was 65-97. So, although it was close, it wasn’t exactly correct. As the season progresses, the Pythagorean record may become more accurate. For the sake of Cub fans, hopefully their defense will as well.