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January 14, 2013

Resident Fantasy Genius

Safeco’s Overstated Impact on Fantasy Production

by Derek Carty

Back in October, the Seattle Mariners announced that they would be moving the fences in at Safeco Field—a notorious (justified or not) pitcher’s park. As a result, fantasy analysts and players are sure to be bumping Mariner hitters up their draft boards and Mariner pitchers down. And, in all likelihood, they’ll be overestimating how much to move those players.

The day after the change was announced, Colin Wyers ran a study to estimate how many additional home runs the change might create. He found that the Mariners and their opponents would likely combine for an additional 22 home runs. Seattle’s internal studies reportedly found that number to be somewhere between 30 and 40. That leaves us with a range of an additional 11 to 20 home runs that the Mariners, as a team, will hit in 2013. Over at the The Book Blog, MGL translated Colin’s numbers to estimate that Safeco’s home run park factor would change from 0.90 to 0.93 from the fence shift.

If you haven’t surmised as much already, these are very small changes. As MGL goes on to say, Safeco, despite its reputation as a deadly destination for power, still only cost “the average full time player for the M’s… less than one home run per year” even prior to the fences coming in. For a Mariner hitter that averages 20 home runs per 650 plate appearances, a ballpark factor change like this would add just 0.3 home runs to his total. Even if you bump it up the high range of Seattle’s cited internal study, we’re still only look at 0.6 round-trippers—maybe a jump from 20 home runs to 21.

The effects, for the average hitter, are negligible. If a free-agent hitter moved from Angel Stadium to Tropicana Field, would you bump up his value, or would you say, “This guy is moving from one moderate pitcher’s park to another, let’s keep him the same”? That’s essentially what’s happening here, except many are going to treat this as if it will add a few extra dollars of value to Mariners slug