Kiko Alonso, MLB, BUF
As Week 1 nears, it seems all but set in stone that Alonso will serve as Buffalo's top linebacker. Nigel Bradham, Manny Lawson and Bryant Scott appear to be fighting for the scraps, as none appears to be particularly close to Alonso's level. Given that there appears to be no one on the Buffalo roster capable of pushing Alonso to the sideline, he looks like a real threat to lead the team in tackles as a rookie. He should be no less than an LB2 in most IDP formats.
Craig Robertson, (3-4) ILB, CLE
Robertson began his career as an undrafted rookie out of lowly North Texas in 2011, but heading into 2013 he's poised to serve as a three-down defender for the Browns. He spent the 2011 season on Cleveland's practice squad before emerging as a strong rotational player in 2012, totaling 93 tackles, one sack and two interceptions despite starting just three games. He's locked into a clear full-time role for Cleveland in 2013, however, and is set to break out as a result. Outside linebackers Jabaal Sheard and Paul Kruger likely will move to defensive end in four-man fronts, leaving just Robertson and D'Qwell Jackson to play the nickel snaps for Cleveland.
John Cyprien, S, JAC
After missing much of training camp with a hamstring injury, Cyprien made his way back onto the field for Jacksonville's last two preseason games. With the injury no longer a concern, Cyprien should be locked into the starting strong safety role for Jacksonville. The 33rd overall pick in the 2013 draft, Cyprien is one of the league's top safety prospects, and his role as a clear starter makes him a decent bet to become a standout IDP in the secondary. He certainly had a nose for the ball in college, making 287 tackles in his final 38 games at Florida International.
Kenny Vaccaro, S, NO
Although he might technically play as a backup to Malcolm Jenkins and Roman Harper, it's evident that Vaccaro will see a huge snap count as a rookie. The Saints might have had the worst defense of all time in 2012 and, with no second-round pick in the 2013 draft, they obviously didn't pick Vaccaro 15th overall if they didn't expect a big immediate impact. When Jenkins and Harper are lined up at safety, Vaccaro is expected to play nickel corner, and the Saints should frequently play in nickel formation in one of the league's most pass-happy divisions. Vaccaro could also earn snaps at Harper's expense in obvious passing situations, as Harper is mostly a one-dimensional run defender. Vaccaro is the Saints' leading tackler through three preseason games with 18, and with Jenkins, Harper and Isa Abdul-Quddus piling up 254 tackles at safety last year, Vaccaro should pile up big tackle numbers himself as he steps in at the position.
Ryan Mundy, S, NYG
With Stevie Brown (ACL) gone for the season, Mundy is expected to step into a starting role opposite Antrel Rolle for the Giants. It's difficult to determine just what the expectations should be for Mundy, as it's the first time he's secured a starting role as he heads into his fifth season. He previously served as a backup for the Steelers, totaling 25 tackles in the five starts he made in those four years. In deeper IDP leagues, though, it's always worth noting a new starter at safety, as they're the defensive backs that most reliably stay near the ball.
Cliff Avril, DE, SEA
Avril was set to play a big snap count for Seattle with Chris Clemons (ACL) questionable for the start of the year and Bruce Irvin suspended for the first four weeks, but it looks like the prized free agent addition from Detroit is on shaky ground himself as the season approaches due to a hamstring issue. He's considered questionable for Week 1, and the lack of a timetable on Avril's recovery leaves one to wonder whether it might be an issue beyond the first week, as well.
Da'Quan Bowers, DE, TB
Bowers is the midst of a rather remarkable descent from where he was two years ago. At one point hyped as a top-five pick in the 2011 draft, the former Clemson star is now at risk of losing his starting role on a Tampa Bay squad that lacks defensive end talent. It's particularly concerning that the reason for Bowers' shaky job security is poor conditioning, which is basically an issue of effort. It seems Daniel T'eo-Nesheim, William Gholston and Steven Means might push Bowers for snaps, limiting his sleeper appeal.
D.J. Williams, MLB, CHI
Williams returned to practice Tuesday as he recovers from a calf injury that sidelined him since July 31, but while he sat on the shelf rookie second-round pick Jon Bostic might have made a compelling push for Williams' starting role at middle linebacker. The Bears obviously didn't draft Bostic in the second round to serve as a backup in the long term, and the Bears are only loosely invested in Williams since he's playing on a one-year deal, so he'll need to safely outplay Bostic to hold him off. Bostic leads the Bears with 12 tackles through three preseason games, including eight tackles (seven solo) in Chicago's dress rehearsal game against Oakland.
Kevin Minter, (3-4) ILB, ARZ
Minter looked like a potential Week 1 starter for Arizona in April when the Cardinals selected him in the second round of the draft, 45th overall, but as the regular season approaches it's not clear how Minter will see the field much on defense. The Cardinals signed free-agents Karlos Dansby and Jasper Brinkley in the offseason, and it seems as if the team is planning to start the two at inside linebacker. When Daryl Washington returns from his four-game suspension, it will be even tougher for Minter to see snaps.
Ezekiel Ansah, DE, DET
Ansah's value is more on hold than it is on the way down, but it's worth noting that he might have suffered a concussion in practice Sunday. If he did, it would mean he's not guaranteed to play in Week 1. Ansah will remain worth holding on to in IDP leagues that go more than 12 deep into the player pool on the defensive line even if he does sit out, though.