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Shutdown defenses II

Posted by Doug on June 22, 2006

Yesterday's post was about how teams did against their opponents' best and second-best wide receivers.

From a fantasy football standpoint, this could be worthwhile information to have. If you can't decide between, say, Steve Smith and Chad Johnson, you might first look at their 2006 slate of opponents and see if one is expected to be playing against tougher pass defenses than the other. If you wanted to dig deeper, you could check to see if one of them is expected to play against defenses that were tougher against wide receivers specifically. Those ideas have been around for a long time. But as far as I know it's not common practice to take it a step further and examine whether Smith or Johnson figures to be playing against a slate of defenses that will be tougher against #1 receivers specifically.

The table at the end of yesterday's post shows enormous variation in how teams fared last year against WR1s and WR2s. Some teams, like the Bears, shut down WR2s while being eaten alive by WR1s. The Redskins, on the other hand, actually allowed more production (in terms of raw numbers) against opposing WR2s than the corresponding WR1s. If these tendencies are caused by personel --- like the mythical shutdown corner --- or by defensive scheme, then we would expect them to persist from year to year. If that's the case, then we've got ourselves a valuable bit of fantasy football information.

But it's not and we don't.

I gathered six years of this data and checked the year-to-year correlation. The correlation coefficient is .10 and is not significantly different from zero. If you don't know what that means, it means roughly this: there is not sufficient evidence to conclude that a team's 2005 "DIFF" will be related in any way to it's 2006 "DIFF." (Yeah, yeah, I know, it merely means it's not related in any linear way.) I guess it's possible that there is some year-to-year carryover among teams that maintain the same coaching staff and mostly the same group of players in the secondary, but that that carryover is being diluted by less stable teams to the point where we can't see it in the data. More likely, in my mind, is that random variation accounts for the differences we saw among teams' relative performances against WR1s and WR2s and random variation will also account for the differences we see in 2006.

This entry was posted on Thursday, June 22nd, 2006 at 4:46 am and is filed under Fantasy. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.