Yesterday I wrote why I thought that the Mariners monthly drop in walks is far more due to changes in the roster construction than because of a change in hitting approach. Today I am bringing up why I think the offense overall has faltered so badly. Sure, the walks have something to do with it, but I don't think it's close to the main reason and I'm not sure main reason has any more grand cause than bad luck.
First, a quick tangent; in my posts about quantifying defense, I brought up the point that BABIP is a useful metric for judging pitchers, because hits allowed is often outside his control and yet has a giant impact on his ERA. However, it's lacking something when applied to defenders and that thing is errors. We don't care about them for pitchers because everyone is tuned to look at ERA and not RA, but errors are a vital component for fielders and, yes, hitters. Some hitters are more able to cause errors than others are and we should credit them for it.
To that end, let me mark down a slightly expanded version of BABIP, which I will label as RBBIP. BABIP, after all, stands for batting average on balls in play. Including errors in the numerator makes this about how often a batter reaches base on balls in play. RBBIP is what I use to judge team defenses against each other and I think it illuminates how the Mariner offense has fallen down.
No American League team reached base more often due to an opponent's error in April than the Mariners and that rate has since been halved. Seventeen Mariner hitters reached via error in April and only 16 have since. The Mariners' BABIP has also fallen consecutively, dropping in May from .279 to .276 and in June to a horrendous .244. Added together and the offense's RBBIP went from .303 in April --good for sixth in the AL-- to .287 in May, which was dead last. June has been even worse at a mere .257, which is not just last, but is last by a good margin.
Now, I'm not sure the Mariners deserved that .303 mark in April over their May or June figures, but just to illustrate the impact a falling RBBIP has, I calculated the difference in run value. If the Mariners had posted a .303 RBBIP in May, they would have had 11 more base runners. A .303 RBBIP in June would have seen a remarkable 27 extra base runners.
Factor those in and here's how the runs per game go:
|Month||Acutal RPG||RBBIP adj RPG|
Again, I am not saying that .303 rate was deserved, only that if it had stayed at that rate, the Mariners offense would have scored about 3.92 runs per game since May 1. If you want something to hang the drop in scoring on, that is where I think it should lay.