By Cian Fahey

Buffalo Bills

Biggest post-draft hole: Offensive line

Losing Mike Pettine may prove to be a massive problem for the Buffalo Bills next year. Pettine's arrival saw the Bills go from the 27th-ranked defense in DVOA during 2012 to the fourth-ranked defense in DVOA during the 2013 season. (DVOA is Football Outsiders' defense-adjusted value over average metric, explained here.) The unit also lost safety Jairus Byrd, but he only started nine games last year when they had the second-ranked pass defense in DVOA.

It's the other side of the ball where the Bills really have a problem.

Adding Sammy Watkins and Mike Williams to the wide receiver depth chart should help improve the passing attack, but little was done to improve the running game. Bryce Brown is a talented running back, but talent at the running back position can only take you so far when the interior of your offensive line is incapable of consistently creating running lanes.

Second-round pick Cyrus Kouandjo should start at right tackle, but he will improve the pass protection more than the running game. Fifth-round pick Cyril Richardson and seventh-round pick Seantrel Henderson, who was an offensive tackle in college, will compete with veterans Kraig Urbik, Chris Williams and Doug Legursky for starting spots inside.

A fully healthy C.J. Spiller, a hungry Brown and a very versatile Watkins should help the Bills revitalize their running game, but they need to get better performances from their interior offensive linemen too.

Notable Undrafted Free Agents

Ohio State quarterback Kenny Guiton was the name that stood out from the Bills' class of undrafted free agents, but he failed to earn a contract after working out for the team after the draft. Instead, the standout undrafted free agent addition is safety Kenny Ladler (Vanderbilt). The Bills added a number of safeties after the draft and Ladler appears to be the most talented. He lacks the long speed to play free safety, but he can be an impact player as an in-the-box safety as well as a contributor on special teams.

Miami Dolphins

Biggest post-draft hole: Linebacker

The Dolphins will likely be starting two rookies (Ja'Wuan James and Billy Turner) and two free agents (Branden Albert and Shelley Smith) on their offensive line this season. A lack of continuity on the offensive line is a major concern, but the Dolphins desperately needed to improve their talent at that spot and they clearly have. If the group is established as the starting line at the start of training camp and stays together throughout the preseason, that chemistry can be created.

If that does happen, then the biggest hole on the Dolphins roster is on the defensive side of the ball.

While the Dolphins have some new faces who are projected to play roles in their secondary, that wasn't the main problem for the unit last season. The Dolphins ranked 12th against the pass last year and were the 29th-worst run defense in DVOA. Jamar Taylor, Will Davis, Walt Aikens, Cortland Finnegan and Louis Delmas could improve the secondary, but the defense will still be dragged down by a problematic trio of starting linebackers.

Unless multiple backups surprise in training camp, Koa Misi, Dannell Ellerbe and Philip Wheeler will start for the Dolphins again this season. Misi is a converted defensive end who has never lived up to his potential on the field no matter where he lines up. Ellerbe and Wheeler were both given big contracts by Jeff Ireland last year, but both proved to be undisciplined and technically deficient as starters.

Regardless of the revamped secondary and the hope that Cameron Wake will be fully healthy this year, the Dolphins simply can't feel good about their projected starters at the linebacker position.

Notable Undrafted Free Agents

The Dolphins should feel satisfied with their efforts in undrafted free agency. They may not have unearthed any stars, but they brought in a number of players who could quickly develop into contributors. Like the draft itself, the undrafted free agent class is highlighted by two offensive linemen: center Tyler Larsen (Utah State) and offensive guard/tackle Evan Finkenburg (Arizona State). Larsen has the talent to develop into a reliable backup behind Mike Pouncey, while Finkenburg is an impressive athlete who played both right guard and left tackle in college.

New England Patriots

Biggest post-draft hole: Depth? Medical staff?

The New England Patriots have a peculiar roster because they don't have one obvious hole. Instead, they have a number of positions with notable question marks. At tight end and defensive tackle, there are major concerns over the durability and expected effectiveness of the most important players. On the interior of the offensive line, there are major concerns over who will be effective next season.

Rob Gronkowski was obviously a major loss when he tore his ACL during last year's regular season. Gronkowski had already entered last year with health problems. He originally fell in the draft because of health question marks. There is a recurring trend with Tom Brady's most important offensive weapon that can't simply be brushed aside. Without Gronkowski, the Patriots' depth chart at the tight end position is underwhelming.

On the interior of the defensive line, each of Tommy Kelly, Vince Wilfork and Dominique Easley are returning from major injuries. Kelly is a 33-year-old who is returning from a torn ACL. Wilfork is a 32-year-old who tore his Achilles tendon last season. Easley has youth on his side at 22, but he hasn't yet played a snap in the NFL and has already torn the ACL in each of his knees.

The offensive line issues are more about performance, not health. Left guard Logan Mankins isn't the player he once was, but it's unlikely that he will be replaced ahead of this season. The same cannot be said for Ryan Wendell and Dan Connolly. Both veterans remain on the roster, but neither is guaranteed anything after underwhelming 2013 seasons and the additions of multiple rookie offensive linemen. Cameron Fleming, Bryan Stork and Jon Halapio were taken in the later rounds of the draft, but without former offensive line coach Dante Scarnecchia, New England's ability to easily plug lower-drafted players into its offensive line may not be what it once was.

Notable Undrafted Free Agents

Although there is some competition for places with more proven players and a player who was actually selected in the 2014 draft, it's hard to look past Stephen Houston (Indiana) as the standout undrafted free agent for the Patriots. Houston is a running back who offers the Patriots some of the same properties that they are losing from LeGarrette Blount's departure in free agency. Blount played a vital role for the Patriots during the second half of the season and starred in their two most convincing victories over the Ravens and the Colts.

New York Jets

Biggest post-draft hole: Outside linebacker

Adding Eric Decker, Jace Amaro and Chris Johnson to the New York Jets offense won't turn the unit into one of the most potent in the NFL, but it should give Geno Smith or Michael Vick a viable supporting cast to be effective in 2014. The Jets could still use a piece or two on the offensive side of the ball, but their biggest hole now resides on Rex Ryan's defense. More specifically, in the front seven.

Calvin Pace is coming off a very strong ten-sack season, but he's 33 and in ten previous seasons he never once managed double-digit sacks. It's unlikely that he will repeat that feat. Pace took the quarterback down 11 times last year—he had two half-sacks—and he didn't beat a block on seven of those plays. On those plays, he was either given a free route to the quarterback or the quarterback left the pocket and Pace brought him down behind the line of scrimmage. On the other sacks, Pace beat one fullback, one tight end (Jimmy Graham), and two offensive tackles (Donald Penn and Tony Pashos).

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Perhaps a more remarkable statistic is that our game charting counted Pace with only six hurries. Every other player with at least eight sacks last season also had at least 14 hurries.

So since Pace doesn't get consistent pressure coming off the edge, it's hard to give him the benefit of the doubt moving forward in terms of expected production. Backup Antwan Barnes is a proven pass rusher, but he is coming off a torn ACL and doesn't offer an all-around skill set. Garrett McIntyre and Jermaine Cunningham are retread veterans who offer little more than serviceable depth.

The Jets have an outstanding defensive line, but with many young pieces moving into bigger roles in the secondary, Pace's presence in the starting lineup becomes a major concern.

Notable Undrafted Free Agents

Terrence Miller, a tight end/wide receiver who didn't produce a huge amount at the University of Arizona, doesn't come across as the most exciting of undrafted free agent additions. However, Miller has good athleticism and excellent size standing at 6-foot-4 and 234 pounds. He needs to learn how to run routes and be more reliable catching the football, but he's definitely an intriguing developmental prospect for an offense that needs to continue creating depth on the offensive side of the ball.

Portions of this article previously appeared on ESPN Insider.