by Vincent Verhei

In a series of articles over the next few days, Football Outsiders will be looking division-by-division at the biggest hole left on each team's roster after free agency and the 2015 NFL draft.

Arizona Cardinals

Biggest Post-Draft Weakness: Offensive Line

This is going to create some controversy. Some observers tabbed Arizona's line as one of the most improved units in the NFL after the Cardinals signed three-time Pro Bowler Mike Iupati away from San Francisco in free agency and then spent their first-round draft choice on Florida's D.J. Humphries. ESPN staff writer Josh Weinfuss even said that Iupati and Jared Veldheer might be the best left side in football.

Our game charters saw things differently -- very, very differently. They credited Veldheer with one blown block every 46.0 snaps played in 2014, ranking 15th-best among left tackles and 30th among all tackles. That's not bad, just eminently mediocre. The real issue, though, is Iupati, whose recent performance on the field has not lived up to his reputation. His rate of one blown block per 37.0 snaps played was 32nd out of 37 qualifying left guards (minimum 400 snaps) and 97th out of 108 interior linemen. This wasn't a one-year fluke, either; in 2013, he had virtually the same rate of blown blocks, one every 36.8 snaps. Between holding penalties and sacks, hits, and hurries allowed, we marked Iupati with 20 blown blocks on pass plays last season. Only one interior linemen had more blown blocks on passes: Ted Larsen, Arizona's left guard last year who will now move over to center.

At the other end of the line, all indications are that Humphries will spend a year on the bench, backing up Bobby Massie, who wasn't terrible last year (42.4 snaps per blown block, 17th among right tackles). Projected right guard Jonathan Cooper was very effective in limited action in 2014 (73.6 snaps per blown block), but he has struggled to stay healthy, with only two starts in his first two seasons.

There is upside here if Iupati can regain his dominant 2012 form, if Cooper can stay healthy, and if Humphries can develop sooner than expected. But man, that's a lot of "ifs."

Notable Undrafted Free Agents: Wide receiver Trevor Harman was a big fish (no, really, he's 6-foot-3, 205 pounds) in a small pond at Division II Shippensburg (go Raiders!), where he set 17 school records. As a junior he caught 105 passes for 1,421 yards and a Division II-leading 22 touchdowns. He's also the nephew of Cardinals coach Bruce Arians. Rob Crisp, a 6-foot-7, 300-pound offensive tackle, was a three-year starter at North Carolina State. Linebacker Edwin Jackson was a first-team All-Sun Belt selection in his senior season at Georgia Southern. Auckland, New Zealand, native Paul Lasike is a former rugby player who never played football until enrolling at BYU. He averaged 4.9 yards per carry in 171 collegiate rushes and added 25 receptions his senior year. Wide receiver Jaxon Shipley, twice named to the Biletnikoff Award watch list, had 218 career receptions (third in school history) for 2,510 yards (sixth) at Texas.

St. Louis Rams

Biggest Post-Draft Weakness: Wide Receiver

The biggest move in the Rams' rebirth as a power-rushing team was the selection of Georgia running back Todd Gurley in the first round of this year's draft, but that was neither the first nor the last part of the process. The trade for Nick Foles gives St. Louis a quarterback who has had success in the NFL as a play-action passer on a run-heavy team. The Rams also let three starters on last year's ineffective offensive line move on in free agency, replacing them with a throw-everything-against-the-wall strategy that saw them take blockers in the second, third, fourth, and sixth rounds of the draft. Along the way, though, the Rams failed to address one of the league's weakest sets of wide receivers. No wideout currently on the Rams roster has ever caught 50 passes or gained 800 yards in a season.

The only Rams wideout to see 50 targets last season (not 50 catches -- 50 targets) was Kenny Britt. It feels like Britt has been in the league forever, but he only turns 27 in December. Britt has averaged 15.6 yards per catch in his career, sixth-best among active players, and has finished in the top ten in that category three times, including last year when he was catching passes from Shaun Hill and Austin Davis. It's not that hard to imagine him flourishing as a long-ball specialist, exploiting defenses that are stuffing the box to stop Gurley.

After that? Well, Brian Quick led the Rams with 53.6 receiving yards per game last year, but only played in seven games. He might not be ready for training camp after separating his shoulder and tearing his rotator cuff in a loss to Kansas City in Week 8. He has only 13 starts in three years on a Rams team that hasn't exactly been spoiled with talent at the position. Tavon Austin is always dangerous on reverses and gadget plays, but he hasn't had much luck actually catching passes. In fact, he had more runs (36) than receptions (31) in 2014. Stedman Bailey was surprisingly effective on a per-target basis last year, but, like Quick, it's telling that he has been such a small part of the Rams' game plan in his first two seasons.

Notable Undrafted Free Agents: The Rams drafted Gurley and have five veteran running backs on the roster, but that didn't stop them from loading up on that position after the draft. Malcolm Brown rushed for 2,678 yards and 27 touchdowns in his career for the Texas Longhorns. Terrence Franks had 712 yards rushing and 11 touchdowns last season at Texas State. Zach Laskey ran for 2,033 yards in his career as a fullback in Georgia Tech's triple-option offense. He could take over as fullback from Cory "the Rams call me a tight end even though my uniform number is 46 and I spend all my time in the backfield" Harkey.

Northwestern State (La.) cornerback Imoan Claiborne was invited to play in the Senior Bowl. Northwest Missouri State defensive end Matt Longacre set school records for sacks and tackles for loss and was named Mid-America defensive player of the year in 2014. Texas Tech wide receiver Bradley Marquez had 65 catches for 821 yards and 10 touchdowns last season, and has also spent two years in the New York Mets' farm system. Iowa defensive tackle Louis Trinca-Pasat went to the Senior Bowl and the scouting combine. He comes from a Romanian family, the youngest of five children and the first born in the United States.

Finally, the Rams signed Clemson wide receiver Daniel Rodriguez, a 27-year-old who earned a Purple Heart serving with the Army in Iraq and Afghanistan. Though his legs were badly damaged by shrapnel in combat, he ran a 4.58-second 40-yard dash at Clemson's Pro Day. His collegiate experience was very limited: he had 11 catches, one run, and seven kick returns in his Tigers career.

San Francisco 49ers

Biggest Post-Draft Weakness: Linebacker

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This figured to be one of San Francisco's greatest strengths in 2015, but then they were undone by a pair of surprise retirements. Five-time All-Pro Patrick Willis, 30, called it a career in mid-March. Though his 2014 season was limited to six games due to a toe injury, he was still effective when healthy, with some of the best pass coverage numbers of any linebacker in the league. In the end, Willis cited his bad feet as the biggest factor in his decision to retire.

If Willis' retirement was unexpected, Chris Borland's departure a week later was stunning. The rookie had 21 defeats (plays that stop an offense on third down, result in a loss of yardage, or force a turnover), ranking in the top 50 in the league, and he did it in only 476 snaps, less than half a season of playing time. Give him a full year, and he might have challenged J.J. Watt's league-leading total of 43 defeats. It was a tantalizing glimpse of what Borland might have delivered in the future, but Borland walked away from the game, citing concerns over possible head trauma. He goes down as perhaps the best one-year player since 1969 Bengals quarterback Greg Cook.

So what's left? NaVorro Bowman is a three-time All-Pro and still only 27 years old, but he missed all of last year after tearing his ACL and MCL in the 2013 NFC Championship Game and only recently returned to practice. Michael Wilhoite started all 16 games last year, but he wasn't much of a factor -- he had fewer run tackles than Borland despite playing more than twice as many snaps. Nick Moody has barely played since the 49ers took him in the sixth round in 2013.

There are question marks on the outside too. Ahmad Brooks has been a rock in San Francisco for four years now, but he missed three games last year and just turned 31. Aldon Smith was a non-factor after his suspension last year, with only two sacks (both against Washington, one of the worst pass-blocking teams in the league) in seven games.

Notable Undrafted Free Agents: The 49ers are also thin at wide receiver, and they loaded up there after the draft with five free agents:

Dres Anderson, Utah: Fifth in school history with 2,077 receiving yards, but only played seven games as a senior following a knee injury.

Issac Blakeney, Duke: In 18 career starts, he had 98 catches for 1,093 yards and 12 touchdowns. He was also on the Blue Devils’ 4x100 track team.

DiAndre Campbell, Washington. Only caught 45 passes for 440 yards and three touchdowns in 52 career games in college.

Darius Davis, Henderson State: The Great American Conference record holder for career receiving yards (3,686) and receiving touchdowns (47), Henderson is old for a rookie (25) and built like a running back (5-foot-11 and 226 pounds; no wideout in the NFL last year was less than 6 feet tall and more than 200 pounds).

DeAndrew White, Alabama: The third option behind Amari Cooper and Kevin Norwood, White finished his Crimson Tide career with 94 receptions for 1,294 yards and 12 scores.

South Carolina's Dylan Thompson is the third quarterback on the roster right now behind Colin Kaepernick and Blaine Gabbert. He led the SEC with a school-record 3,564 passing yards last season, and also threw 26 touchdowns.

Seattle Seahawks

Biggest Post-Draft Weakness: Offensive line

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By Football Outsiders' numbers, Seattle's rushing offense last season was best in the league by a wide margin and one of the five best in our database going back to 1989. That says more about the singular brilliance of Marshawn Lynch, though, than it does about Seattle's line. By our count, Lynch broke 29 more tackles than any other player in the league last year, and the effect of those broken tackles was dramatic. ESPN Stats & Information data shows that out of the 43 backs with at least 100 runs last year, Lynch was second with 2.5 yards after contact per carry, but his 2.2 yards before contact was just 22nd. That latter ranking is much more indicative of the offensive line's run-blocking prowess, and they were even worse at pass blocking. Russell Wilson was pressured on 39 percent of his dropbacks last season, the highest rate of any starting quarterback. Rookie right tackle Justin Britt somehow managed to lead the NFL in blown blocks on passing plays even though Seattle had the fewest dropbacks in the NFL.

So Seattle's line was on shaky footing anyway, and then it lost center Max Unger in the Jimmy Graham trade, while left guard James Carpenter signed with the Jets in free agency. The Seahawks have no proven options to replace them. Of the candidates on hand, Lemuel Jeanpierre has seen the most action with 11 career NFL starts (including three last year at center), while Alvin Bailey (three starts at guard last year, two at tackle) and Patrick Lewis (four starts at center) never started a game before 2014. All three came to Seattle undrafted. The Seahawks did add a couple of blockers in the fourth round of this year's draft, San Diego State's Terry Poole and West Virginia's Mark Glowinski. They also grabbed Buffalo's Kristjan Sokoli in the sixth round, but the collegiate defensive lineman looks like more of a long-term project than a first-day savior. That's a lot of question marks for a team looking to play in a third straight Super Bowl.

Notable Undrafted Free Agents: Nate Boyer may be the most famous long snapper in the NFL, and he hasn't even had a full practice yet. The 34-year-old former Green Beret earned a bronze star after tours in Iraq and Afghanistan, and taught himself to long snap by throwing a ball between his legs to nobody in Afghan dirt fields, all while volunteering to serve in the most dangerous locations available. He is the longest of long shots to make the team -- he's only 5-foot-10 and 195 pounds, and Clint Gresham, the team's long snapper since 2010, just signed a three-year, $2.7 million contract -- but you won't find a better Cinderella story this year.

Norfolk State strong safety Keenan Lambert is the half-brother of Seahawks star Kam Chancellor, and the two grew up sharing a bedroom. Unfortunately freakish size (for a defensive back) does not run in the family; Lambert is 3 inches shorter and 23 pounds lighter than his big brother. Idaho offensive tackle Jesse Davis also has experience at defensive tackle and tight end, so he might join the list of converts on Seattle's offensive line that also includes starter J.R. Sweezy. Other conversion projects include Trovon Reed (an Auburn cornerback who, like Richard Sherman, started his collegiate career as a wide receiver) and Tory Slater (a 290-pound defensive end out of West Georgia who played wide receiver in high school, though he is now on injured reserve). Texas-San Antonio's Triston Wade, a Jim Thorpe Award finalist, is an undersized free safety (5-foot-11 and 170 pounds) with a penchant for flying around and making plays -- which sounds like a perfect backup for Earl Thomas. Arizona wideout Austin Hill projected as a fourth- or fifth-round pick; at 6-foot-3 and 210 pounds, he could be the big receiver Seattle is looking for.

Portions of this article originally appeared at ESPN Insider.