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 Options
The chalk this week is going to be Buffalo, Baltimore and Houston. All three teams are home favorites, and their opponents have three of the four lowest implied totals this weekend. Of these three, Baltimore is by far the best defense as they rank second in Football Outsiders' Defense Efficiency Ratings (DVOA). Buffalo and Houston have the better matchups against Cleveland and Jacksonville, both of whom rank in the top five of friendliest fantasy matchups for opposing defenses. But Baltimore's matchup with Philly isn't a bad one as the Eagles have been a slightly above average matchup for fantasy defenses this season.
Perhaps more important than matchup is the fact that Buffalo and Houston's defenses just aren't on the same level of Baltimore's. Buffalo ranks 22nd in DVOA, and Houston ranks 13th. However, the Texans rank 19th in the weighted version of DVOA (Buffalo is still 22nd in weighted DVOA), so Houston and Buffalo are really below average defenses. Yeah, their matchups are good, but Baltimore's isn't bad and the Ravens are a superior defense. Not to mention the fact that the Ravens are noticeably cheaper than both the Texans and Bills defenses on both DraftKings and FanDuel. If you're going for chalk in cash games, Baltimore is the play.
Sneaky Options
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 two teams that best fit that bill this week are New York and Denver. The Giants rank fourth in DVOA and third in weighted DVOA, and we all saw how good their defense looked on Sunday night against Dallas. The Giants are home favorite this week against the Lions who have the fifth lowest implied total of teams playing on Sunday. For the season the Lions have been a below average fantasy matchup for opposing defenses, but they’re not such a bad matchup that the Giants can’t be considered as a GPP option. So, the giants check the Vegas boxes (home favorite, opponent with low implied total), they’re a good defensive unit, and they figure to see ownership easily in the single digits.
The other option here is Denver who will host New England. There’s no question that New England is one of the five or six teams in the league who is a very bad matchup for opposing defenses, but don’t forget how good Denver’s D is. The Broncos rank first in both DVOA for the season and in the weighted version. And the Pats have averaged just under 20 points per game in three trips to Denver in the last three seasons, so there’s some history there to indicate the Broncos D can have a decent game here. But the main point here is the Denver rates as the best defense in the league and is basically going to be unowned, and you rarely get to make such a contrarian play with such a good defense.
Bargain Option
If you’re trying to go as cheap as you can on either site, Jacksonville continues to be an appealing cheap option week after week. For one thing, the Jags D is above average as they rank 15th in DVOA and 13th in the weighted version. They also have a very nice matchup against Houston this weekend. The Texans have allowed the ninth most fantasy points per game to opposing defenses, and they have the second highest interception rate among teams in action on Sunday. Sure, the game is in Houston and the Texans are favored, but you’re not going to find an ideal set of circumstances with a defense as cheap as Jacksonville’s.