The Strategy of Rotating Defenses Week by Week

I have always held to the belief that it's not worth it to draft a defense early. I figure you can always snipe one of the upcoming units from the free agent pool or change your defense depending on matchups each week. I'll always wait until the 3rd to the last round at least before drafting a defense, and might not draft one at all (instead I'll look to make a multiplayer trade before the season starts then pick up a defense off the free agent pile).

In a couple leagues this season, I rotate my defense every week, rotating mediocre defenses from the free agent pool depending on the matchup. I always do this in salary cap as well.

How does this strategy of rotating defenses week by week compare to sticking with one dominant defense the whole season? To look at this, I'll compare the best defenses in terms of interceptions made and sacks made with the worst offenses in terms of interceptions thrown and sacks allowed last year.

Note that this clearly doesn't include some important statistics when looking at defensive units, but this should still be a fairly accurate comparison. As you can see, for top defenses, the rank according to merely interceptions and sacks correlates well with their actual fantasy rank for the season.

2007 Top 10 Defenses in terms of Interceptions and Sacks

Team	Int	Sacks	Sacks+2*Int	Actual Fantasy Rank
San Diego	30	42	102	1
New England	19	47	85	3
Seattle	20	45	85	4
Dallas	19	46	84	5
Tennessee	22	40	84	9
New York	15	53	83	8
Jacksonville	20	37	77	14
Green Bay	19	36	74	11
Chicago	16	41	73	6
Indianapolis	22	28	72	10

2007 10 Worst Offenses in terms of Interceptions and Sacks

Team	Int	Sack	Sacks+2*Int
St. Louis	28	48	104
Detroit	22	54	98
Kansas City	20	55	95
NY Jets	19	53	91
San Francisco	17	55	89
Chicago	21	43	85
Oakland	20	41	81
Philadelphia	15	49	79
Atlanta	15	47	77
Pittsburgh	14	47	75

The tables above show that generally, the number of points you should expect from your defense in any given week is more dependent on how good the offense you are facing is rather than how good your defense is.

So if you like to plug in defenses week by week depending on the matchup, let these tables support your tactics. Meanwhile, if you like to draft defenses early, it's time to rethink your strategy.

If you still think that drafting defenses early is a good idea and want to shrug off the conclusion of the above tables since they sample only one year, consider that the performances of defenses vary significantly from year to year and that you can often pick up a good defense during the year anyways. Make sure you wait until you draft a defense next year.