I'm one of the 10 or so weirdos on the planet who has a passion for D/STs. In truth, it's a difficult passion to explain to people. Fantasy football is already a niche within a niche, and defensive streaming adds a couple of layers of obscure on top of that. Indeed, even a certain chunk of the fantasy football community is vehemently opposed to defensive streaming.
Whether you share my passion for the D/ST position, or you're gritting your teeth and bearing with your league's decision to keep the spot in spite of your repeated requests to the contrary, I'm here to help.
A few housekeeping matters: lines are courtesy of NFL odds, and roster percentages and scores are from the Yahoo! fantasy platform. Assume that the listed order is the preferred order. I'll try for defenses on 40% or fewer of Yahoo rosters.
Tennessee Titans
at Houston Texans
Spread: Titans -10.5
Roster Percentage: 42%
The Tennessee Titans are once again a premium streaming option in Week 18. The Houston Texans have just a 16.25-point implied total in Week 18. Davis Mills is still getting sacked (7.4% rate) and intercepted (2.8% rate) at high clips.
The Titans have top 10 defensive unit at in terms of Net Expected Points (NEP) allowed per play (0.04). Surely, the Texans should be overmatched in this game that Tennessee needs to clinch the top overall seed.
The Titans, according to our model, are the fifth-highest projected D/ST in Week 18.
Washington Football Team
at New York Giants
Spread: WFT -6.5
Roster Percentage: 25%
The Washington Football Team has one of the weaker defensive units in the league at (0.16 Defensive NEP per play), but drawing Jake Fromm in Week 18 should be sufficient to make them look like world-beaters.
The New York Giants actually have a lower implied point total (16.0) than the Texans. the struggling Bears unit scored four takeaways and five sacks, and in fact, the G-Men's 11.3 points per game allowed to opposing D/STs is all the way up to the third-most in the NFL
Fromm hasn't played enough in the NFL to know his true limitations, but his inability to separate from Mike Glennon should lead to a safe assumption that he's not great, and Fromm has done nothing but validate that assumption in limited action.
Minnesota Vikings
vs. Chicago Bears
Spread: Vikings -2.5
Roster Percentage: 27%
Likely having Sean Mannion under center is something of a setback for the Minnesota Vikings, but they're still slight favorites in Week 18.
Justin Fields brings his 11.8% sack rate and 3.7% interception rate to one last fantasy opponent this season, and as always, that makes the opposing D/ST an appealing streamer.
The Vikings have an average defensive unit in terms of Defensive NEP per play (0.11). However, they're a safe option; they've scored at least five points in 12 of their 14 games that weren't facing the deadly Aaron Rodgers-led Packers.