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The Home Runs Happened

Alternate title: Surprise! Dingers!

Some time ago, we observed that the Mariner relievers were succeeding in no small part because they were avoiding home runs. Avoiding home runs to what certainly appeared to be an unsustainable degree. It was good, because those innings were already in the books and you can't retroactively apply home runs later on, but it was worrisome, because it left us wondering what would happen if and when the dingers showed up.

The dingers showed up. Two tables of bullpen data:


Stat Mariners League
BB% 8.6% 10%
K% 16% 19%
HR% 0.9% 2.3%
R/9 3.87 4.38


Stat Mariners League
BB% 7.9% 8.5%
K% 14% 21%
HR% 3.4% 2.5%
R/9 4.23 3.80

Earlier, the Mariners' bullpen home run rate was well above-average, and they maintained a R/9 that was 12% better than the league. More lately, the home run rate has gone in the other direction, and the R/9 has been 11% worse than the league. Not that R/9 is the perfect measure with samples this small, but the point gets across. After allowing five total home runs in April and May, Mariner relievers have allowed nine home runs since the start of June, and they've caused some real trouble as a consequence.

The good news is that, just as the early home run suppression was unsustainable, the recent home run inflation is also unsustainable, especially given that the Mariner bullpen runs the highest groundball rate in the American League. Even if and when the personnel changes, the longballs should be less frequent.

So what we have overall is a bullpen that, in truth, is neither a strength nor a weakness. I don't know how much this matters, given the Mariners' place in the standings, and I don't know how much it's going to change if pitchers break down or other pitchers break in, but given everything that didn't go according to plan with David Aardsma, Shawn Kelley, Josh Lueke and Dan Cortes, it seems like a small miracle that the relief is still all right.