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Matt's must-start fantasy football waiver wire defenses (D/ST) to stream and start for Week 18 of the 2025 season. His fantasy defense start 'em, sit 'em picks.
While the majority of fantasy football championships were decided last week, there are a few brave souls still competing for league titles in Week 18, as well as DFS grinders who are looking for the perfect option at the D/ST spot. RotoBaller's Matt Donnelly is here to help you lock up a trophy with his top Defense (D/ST) Must Starts for Week 18!
We've got you covered with Week 18 D/ST streamer options to give you the tools needed to set those winning lineups and dominate your matchups in the fantasy playoffs!
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2025 Fantasy Football: Week 18 Defenses To Start (D/ST)
Matt Donnelly drops his top Defenses for Week 18 of the 2025 fantasy football season:
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Week 18 Fantasy Football Defense Outlooks
Kansas City Chiefs D/ST at LV
Fantasy managers looking for high-floor defensive options this week should look toward the Chiefs. This unit will have the best matchup of the week against a Raiders offense that will likely be starting Kenny Pickett this week. Geno Smith left last week's game due to an ankle injury, and the Raiders won't risk playing him in a meaningless game.
Therefore, this Chiefs D/ST is a nice play in all formats. Las Vegas has given up a league-leading 61 sacks, and Kansas City actually shut out Las Vegas in its first meeting this season. Given that Pickett threw for 64 yards and one interception in his one start this year, this Chiefs defense is trustworthy to start in Week 18.
Jacksonville Jaguars D/ST vs. TEN
The Jacksonville Jaguars have been one of the more impressive fantasy defenses in 2025. They have scored the sixth-most fantasy points among all D/ST this year and have allowed 20 points or fewer in seven straight games. So, the Jaguars are worth a look in most leagues with a matchup against the Titans on the horizon.
Although Cam Ward has played better over the past month, this is still an offensive line that allows sacks at an extremely high rate. Ward was sacked four times in last week's loss to the Saints. Given that Jacksonville has totaled multiple sacks in seven of its past nine games, this D/ST will be a solid start in most leagues.
Buffalo Bills D/ST vs. NYJ
Brady Cook is set to make his fourth career start in Week 18. In his previous three starts, Cook has thrown five interceptions while being sacked 12 times. That makes this Buffalo D/ST a must-start unit in fantasy football championships. Although this defense has been very up-and-down this season, it's hard not to trust this group this week.
The Jets have given up the second-most sacks (59) in the NFL this season and currently rank 26th in pass block win rate. With the Bills totaling at least three sacks in two of their last three games, this D/ST has some sack upside in this contest. Just two weeks ago, Cook was sacked eight times in a loss to the New Orleans Saints.
Houston Texans D/ST vs. IND
The Houston Texans will come in as the best fantasy defense for Week 18. This unit has given up the fewest points in the NFL this season and has allowed over 20 points in a game just once since Week 11. With Riley Leonard starting for the Colts this week, this Houston D/ST should be started in all formats.
The Texans have totaled the fifth-most sacks in the NFL through 17 weeks and have one of the most formidable pass rush duos in Will Anderson Jr. and Danielle Hunter. Considering the Colts rank 29th in pass block win rate, this Houston defense should be in for a strong defensive performance. This group has tallied multiple sacks in seven of its last eight games.
Baltimore Ravens D/ST at PIT
The Ravens D/ST has some potential in Week 18 against the Steelers. With DK Metcalf still suspended and Calvin Austin III nursing a hamstring injury, the Steelers could struggle to move the ball on offense once again. However, after this Baltimore defense just allowed Pittsburgh to score 27 points while totaling zero sacks a few weeks ago, this D/ST will come in at the bottom of tier 3.
Week 18 D/ST Rankings
| Rank | Player Name |
| 1 | Houston Texans |
| 2 | New England Patriots |
| 3 | Jacksonville Jaguars |
| 4 | Denver Broncos |
| 5 | Buffalo Bills |
| 6 | Philadelphia Eagles |
| 7 | Los Angeles Rams |
| 8 | Green Bay Packers |
| 9 | Minnesota Vikings |
| 10 | Kansas City Chiefs |
| 11 | Seattle Seahawks |
| 12 | Cincinnati Bengals |
| 13 | Baltimore Ravens |
| 14 | Carolina Panthers |
| 15 | New Orleans Saints |
| 16 | Atlanta Falcons |
| 17 | Los Angeles Chargers |
| 18 | Tampa Bay Buccaneers |
| 19 | Pittsburgh Steelers |
| 20 | Chicago Bears |
| 21 | Dallas Cowboys |
| 22 | Las Vegas Raiders |
| 23 | Cleveland Browns |
| 24 | San Francisco 49ers |
| 25 | Detroit Lions |
| 26 | New York Giants |
| 27 | Indianapolis Colts |
| 28 | Miami Dolphins |
| 29 | Tennessee Titans |
| 30 | Washington Commanders |
| 31 | New York Jets |
| 32 | Arizona Cardinals |
Who Should I Start Tool
Not sure who to start? Check out the Who Should I Start tool:
Compare up to four players and we'll tell you who to start...
Who Should I Start? Who Should I Sit? Some common Week 18 fantasy football lineup decisions are regarding defenses like the Kansas City Chiefs, Baltimore Ravens, Jacksonville Jaguars, Houston Texans, Buffalo Bills, and more. But not to worry, we are here to help make these decisions and build winning lineups in Week 18. Set your optimal fantasy football lineups for Week 18 of the 2025 NFL season. Our free Who Should I Start? tool will help make your fantasy football lineup decisions. Compare up to four NFL players, and we tell you who to start... all free! Get your winning lineups set, and make the right decisions.
Week 18 Player Decisions. Today's focus is on specific defenses like the Kansas City Chiefs, Baltimore Ravens, Jacksonville Jaguars, Houston Texans, Buffalo Bills and more. These are some of the most common searches for fantasy football lineups in Week 18.
Using The Tool. This is a simple tool but very powerful. The first step is to enter the player names that you want to compare. In the first box, search for the first player name. In the second box, search for the second player name. Compare up to four NFL players at once, and then click the Who To Start? button to see who the recommended starts are based on weekly fantasy football matchups.
Improvements For Who Should I Start? You may have noticed, our Who Should I Start? tool has gotten an overhaul. We've added lots of great features for you to give you as much information as possible to win your fantasy football matchups each week. You'll see NFL player tiles with headshots and bye weeks, enhanced search results with data to compare, and a slick new interface. We hope you enjoy!
How It Works. Each week, our RotoBaller staff puts together their weekly fantasy football rankings and projections based on their research. That information is the core data that is powering the decision-making in this tool. When you search for player names, you will only see those players who are ranked. If someone is out for the week, they will not appear in the search results.
Scoring Formats. Fantasy football managers play in various types of leagues, and this tool allows you to choose whether it's PPR scoring, Half-PPR scoring, or Standard (Non-PPR) scoring. The second thing you want to do is to select the scoring format. There are three small radio buttons (small circle), so click on the scoring format you prefer. The results may vary based on the scoring format you select.
Popular Week 18 Searches. Curious to see some tough lineup decisions for Week 18 (2025)? Below you will find a list of some popular Who Should I Start? searches that RotoBaller readers are looking at this week. Click any of the links to see the result and recommendation.
Popular Week 18 Searches - Start/Sit Player Comparisons
Below are some popular Week 18 searches and comparisons from our 'Who To Start' tool for the compared to others:
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