The key with defenses is finding defenses that will face a lot of passing plays. Fantasy point-scoring events like interceptions and sacks occur exclusively on passing plays, and fumbles actually occur more on passing plays than running plays. Defensive touchdowns are difficult to predict, but they're also more likely to occur on passing plays with 53 pick sixes last year compared to only 33 scoop 'n scores.
One of the best ways to identify defenses that will face a lot of passing plays is identifying Vegas favorites, preferably home favorites. And obviously the lower the opponent's implied point total, the better the matchup for the defense.
Premium Option
The chalk this week is unquestionably Arizona. The Cards will host the 49ers who have allowed the third most fantasy points per game to opposing defenses so far. The Niners have the lowest implied total of the weekend, and they're gigantic 13.5-point underdogs in Arizona. The Cards defense ranks third in Football Outsiders' defense efficiency ratings (DVOA), and they're top 10 against both the run and the pass. Our Ownership Forecaster expects their ownership percentage to be more than double any other defense on both sites. So fire them up all you want in cash games, but feel free to get contrarian in GPPs and look elsewhere.
Sneaky Option
This category is reserved for good defenses that may be overlooked in a given week for whatever reason, providing you with the opportunity to roster a really good unit with a lower ownership rate.
The Ownership Forecaster projects Marcus Mariota to be the most heavily owned quarterback this weekend, which means the Green Bay defense certainly can't be an obvious play. But there are reasons to like the Packers defense. They rank seventh in DVOA (eighth in the weighted version), and they're ranked sixth against the run. Their pass defense is their supposed weakness, but they're average on the back end ranking 16th in pass DVOA. Tennessee has been a good matchup for opposing defenses this year as they've allowed the fifth most fantasy points per game to opposing defenses. Every defense that has faced Tennessee that wasn't Cleveland or Jacksonville scored at least six fantasy points when they played the Titans. So don't sleep on the top 10 defense who is a favorite against one of the best matchups for fantasy defenses this season.
Bargain Options
The cheapest options you can stomach on DK this Sunday are New York and San Diego. The Jets don't have a great defense as they rank 24th in DVOA, but they're a home favorite this week against the Rams who have the second lowest implied total of the week. The Rams have allowed the second most fantasy points per game to opposing defenses, and all but one defense that has faced them scored at least seven fantasy points.
The Chargers are a good defense as they rank eighth in DVOA, but their matchup isn't as good as New York's as they'll host Miami. The Dolphins rank mid-pack in terms of fantasy points allowed to opposing defenses, and they only have a slightly below average implied team total this weekend. The Chargers are projected to be owned more than the Jets, so if you're playing GPPs the Jets make more sense as a cheap DK defense. But if you're playing cash games and need to save at DST, it would be understandable if you went with the better defense with the Chargers.
Over on FD the cheapest option you should be able to live with is Washington. Washington is very much like the Jets in that they don't have a great defense, but they do have a great matchup. They rank 21st in DVOA, but they're a three-point home favorite against the Vikings, who have given up 40 fantasy points to opposing defenses in their last three games. The Vikes have the third lowest implied total on Sunday, so the Redskins are a nice value against them as the eighth cheapest DST on FD.