Fantasy football defenses can be hard to evaluate. It often depends on the teams matchup and switching defenses out week to week is the way to go. You’re going to want a powerhouse defenses that’ll rack up sacks and turnovers. But you don’t necessarily need a defense that gets shutouts, because a sack or two is worth the same amount of fantasy football points as holding an opponent to 17 points or less.

Confusing, right?

There are a couple of them out there worth a mid to low round selection. In short, don’t go to high and take one in the top six or seven rounds, just wait until near the end. Here are the top five defenses fantasy-wise for 2015:

1. Buffalo Bills

via buffalorumblings.com

via buffalorumblings.com

The No. 1 fantasy defense in 2014 added a defensive-minded head coach in Rex Ryan. They led the league with 54 sacks last season, and Ryan did not retain Jim Schwartz as defensive coordinator. This team has arguably more talent up front then Ryan’s early New York Jets teams, so 55 to 60 sacks is in range. They don’t have the highest upside, but are a very, very safe pick.

2. Miami Dolphins

via foxsports.com

via foxsports.com

The addition of Ndamukong Suh to a line that already had Cameron Wake and Olivier Vernon could bring the Dolphins to compete with the Bills d-line. Last season they had at least 10 points in six of their first eight games, but faded horribly down the stretch. Brent Grimes and Loius Delmas hold up the secondary and if they replicate what they did over the first half of 2014 (with Suh in the mix making everyone better) they will be a top fantasy defense.

3. Seattle Seahawks

via Rantsports.com

via Rantsports.com

The usual consensus first defense drafter, they fell to three on this list because Earl Thomas might miss some time to start the year with his torn labrum and Byron Maxwell has left. Cary Williams is slated to take his place as a starter, and while he’s had a lot of success, he’s gotten burned a few times as well. This unit still has the highest upside and their performance down the stretch of last year was dominant.

4. Baltimore Ravens

via pressboxonline.com

via pressboxonline.com

The Ravens had 49 sacks last season and the duo of Elvis Dummervill and Terrell Suggs may be the best in the league. C.J. Mosley is coming of a great rookie year and Darryl Smith is still successfully fighting off father time. The Ravens will continue to get to the quarterback and stack up points.

5. Houston Texans

via rantsports.com

via rantsports.com

How much damage will J.J. Watt do? The Texans finished fourth in fantasy scoring last season and as long as Watt continues his terror, the rest of the defense will hold up behind him. They added Vince Wilfork in the middle and Brian Cushing will look to bounce back from a down year. Don’t forget about Jadeveon Clowney. Anything they get from him coming of micro fracture surgery will be a bonus. The Texans will be a top-five defense this fantasy season.

Other fantasy football rankings

Top 10 fantasy football quarterbacks of 2015

Top 10 fantasy football running backs of 2015

Top 10 fantasy football wide receivers of 2015

Top 5 fantasy football tight ends of 2015