Jamie Collins, OLB, NE
An unspecified virus kept Collins out of the last five games for New England, but he's loosely expected to return to the field against the Eagles this week. When healthy, Collins is one of the league's truly elite defenders, a top-five real life linebacker who has the potential to rank similarly as an IDP. He entered the league as a dominant, hyper-athletic edge rusher from Southern Mississippi, but he turned into an all-around, off-ball linebacker for the Patriots, all while still possessing lethal explosiveness as an edge rusher. Indeed, in his first seven games of 2015 Collins posted 51 tackles (29 solo, four for a loss) while adding 4.5 sacks and three forced fumbles. If he could maintain that pace over a 16-game sample, it would project to about 117 tackles and 10.5 sacks – a figure that likely isn't sustainable, but nonetheless illustrative of Collins' truly rare upside as a dual tackle-sack threat.
Tyrann Mathieu, S, ARZ
It took until his third season, but it appears that Mathieu has at last arrived, and he's consistently showing glimpses of the incomparable playmaking skills that made him such a marvel at LSU. After a monstrous 13-tackle, one-interception game against the 49ers on Sunday, Mathieu is now up to 70 tackles, one sack, four interceptions and one touchdown in 11 games. There aren't three more desirable defensive back IDPs at this point, and what's scary is that Mathieu still has room to grow in his game, especially if he starts to show the blitzing and fumble-forcing ability he showed in college. Although he played only two years for the Tigers, Mathieu definitively established himself as one of the best college football defenders of all time, largely because he posted six sacks and 11 forced fumbles in just 26 games as a cornerback.
Manti Te'o, (3-4) ILB, SD
Back from an ankle injury that cost him four games, Te'o has been quite good over the last two weeks and has made clear by now that former top inside linebacker Donald Butler is a thing of the past in San Diego. Playing alongside rookie second-round pick Denzel Perryman, Te'o has been a useful IDP whenever active this season, totaling 52 tackles (38 solo, four for a loss), one sack and one interception in seven games. That would project to roughly 119 tackles, two sacks and two interceptions over the course of 16 games, putting Te'o in LB2 territory until further notice.
Tony Steward, LB, BUF
With Nigel Bradham (ankle) expected to miss Sunday's game against Houston, Steward is expected to step into the starting lineup for Buffalo. That Steward almost hasn't played at all – just four defensive snaps – is obviously a concern, and one that probably limits him to a streaming option in only deeper IDP formats. On the other hand, Bradham's role at least comes with a big snap count – Bradham played on over 95 percent of Buffalo's defensive snaps heading into this week. With 4.6 speed, Steward has the range to stalk ballcarriers, and it appears he'll have the opportunity to do so.
Kyle Williams, DT, BUF
Williams was unable to make much of a statistical impact in an ill-conceived Buffalo defensive scheme – more on that in a moment – but it's injury that will definitively reduce William's 2015 to a wasted season. With just 14 tackles (six solo) and one sack in six games, the 32-year-old defensive tackle's season ends due to a meniscus injury. Like all of himself, Mario Williams, Marcell Dareus, and Jerry Hughes, it's hard to see the potential for anyone to produce in the Rex Ryan-devised trainwreck that is the Buffalo defense.
Mario Williams, DE, BUF
I fell for it perhaps worse than anyone, but when Rex Ryan joined the Bills the belief was that Ryan, always known as a 3-4 student, would display the knowledge and pragmatism necessary to leave the Bills in a 4-3 alignment while yielding similar or better results than those preceding Ryan's arrival. The reason for that assumption was simple enough – Ryan always appeared a defensive genius before, and Buffalo's personnel was entirely incompatible with the 3-4. Be it a lack of pragmatism or the inability to devise a functional 4-3 alignment, Ryan has instead shown a complete inability to get any decent results out of a Buffalo front seven loaded with talent, especially among the linemen. Williams has been the most visible disappointment, totaling 14 tackles and three sacks in 10 games, but Jerry Hughes and Marcell Dareus have also struggled.
D.J. Hayden, CB, OAK
Not many people liked the pick when Oakland shockingly selected Hayden 12th overall in 2013, and no one likes the pick by now. Hayden was benched a week ago, and not for just any cornerback – he was benched for David Amerson, one of the most infamous burn artists among recent defensive backs. If that's not bad enough, consider then that Amerson proved an upgrade in his first game. Hayden's burn rate made him a decent tackle source for a corner – 56 in 10 games – but a burn tendency can obviously get a cornerback benched, and at this point Hayden's owners will have to find tackles elsewhere.
Ryan Shazier, (3-4) ILB, PIT
Although his injuries are generally unrelated and seem unlucky rather than chronic, it's becoming more and more difficult to stand by Shazier, who has yet to make a sustained impact in the NFL since the Steelers drafted him 15th overall in 2014. After a shoulder injury knocked him out for four weeks, Shazier played four games before picking up a knee tweak, and then he suffered a concussion against the Seahawks on Sunday, leaving him questionable for this week. Shazier is the NFL's most athletic linebacker and has huge upside – he has 47 tackles (nine for a loss) and three sacks in six games this year – but the durability needs to be more reliable for fantasy owners to capitalize.