NFL rosters are primarily built, torn down, replenished and picked over in March and April. Every year, several teams hit the jackpot in free agency, and several more usually do the same in the draft. And every year, just as many teams typically encounter calamities during those distinct periods. 

We're here today for the March calamities. 

Here's a look at a handful of NFL franchises that are on track to either lose a ton of talent without the ability to replace key departures or overspend and strike out on some of the market's most expensive commodities. 

Minnesota Vikings

Spotrac estimates that the Minnesota Vikings are over the projected salary cap by more than $12 million, which leaves them more than $10 million behind the second-lowest-ranked team in terms of cap space. 

That's not always indicative of how a team's offseason will go, because everybody can trim some fat and not everybody needs to participate heavily in free agency. The Vikings do have plenty of talent as is, they'll save $14.5 million when edge-defender Everson Griffen comes off the books soon, and they can save another $18.6 million by parting ways with veteran defenders Xavier Rhodes and Linval Joseph.

The problem is that leaves them without a star pass-rusher, a well-accomplished starting cornerback and a defensive tackle who has started 88 games in Minnesota since 2014. And it still leaves them with extremely limited funds for impending free-agent defensive backs Anthony Harris, Mackensie Alexander and Trae Waynes. 

The Vikings pass defense was a weak spot in 2019, and Harris, Alexander and Waynes were their three best players in the secondary not named Harrison Smith. There's a chance they'll lose at least two of them along with Rhodes, and retaining Griffen will also be a tremendous challenge. 

Minnesota is a good-not-great 18-13-1 since signing quarterback Kirk Cousins in 2018, and when April arrives, the Vikes are likely to be in worse shape than they are now. That'll put a lot of pressure on general manager Rick Spielman in the draft. 

Pittsburgh Steelers

The straits aren't as dire with the Pittsburgh Steelers, but they, too, are in the red when it comes to the salary cap, and it'll be more difficult for Pittsburgh to find fat to trim. 

They only need to chop about $2 million from the payroll to get back into the green, but there are very few cut candidates making more than $5 million a year. Even if they rework some contracts and collect more than $15 million by waving goodbye to veteran tight end Vance McDonald ($5.7 million) and linebackers Anthony Chickillo and Mark Barron (a combined $10.3 million), it'll be almost impossible to keep key impending free-agent front-seven defenders Bud Dupree and Javon Hargrave. 

Dupree was one of just four NFL players to register more than 10 sacks and more than three forced fumbles in 2019. His departure could make it easier for opponents to block T.J. Watt on the edge. Meanwhile, Hargrave's Pro Football Focus pressure rate of 14.2 percent ranked behind only superstars Aaron Donald and Chris Jones at the defensive tackle position. 

Both would be dearly missed. And if the Steelers find a way to retain those guys, they'll likely create holes elsewhere without addressing offensive needs like tight end, wide receiver and possibly even the interior offensive line considering that Ramon Foster is 34 and David DeCastro and Maurkice Pouncey are both 30. 

Making matters worse, they have just one pick in the first three rounds of the draft. 

Los Angeles Rams

The Los Angeles Rams at least have room to breathe with a projected $23 million in salary-cap space, but L.A. might actually have more work to do than Minnesota and Pittsburgh. 

Longtime left tackle Andrew Whitworth, top edge-rusher Dante Fowler Jr., superb linebacker Cory Littleton and veteran defensive line starter Michael Brockers are all slated to hit free agency next month.

But even if the Rams keep some of those key players, the offensive line needs plenty of additional work. 

Guard Austin Blythe, who struggled in 2019, also has an expiring contract. He'll either have to be re-signed or replaced, and they desperately need upgrades at right tackle and the opposite guard position. And that'll be a nearly impossible task under these circumstances, especially considering that—like the Steelers—they lack a first-round pick. 

This stems from the fact that the Rams are on the hook for a combined 2020 cap hit of $53.3 for quarterback Jared Goff and running back Todd Gurley, both of whom disappointed last season. They can save a few bucks by moving on from Gurley, and NFL Network's Ian Rapoport reported recently that the team plans to meet with Gurley soon to discuss his future.

If a divorce were to come to fruition, that move alone would put an embarrassing damper on L.A.'s offseason pursuits. 

Tennessee Titans

The Tennessee Titans are pegged to possess nearly $50 million in cap space, so money isn't an issue. The problem is they have more in-house free-agency work to do than almost any team in football, and they're going to have to make some extremely expensive decisions that have a high probability of backfiring. 

After an unreal and unexpected run to the AFC Championship Game, the organization will likely feel emotionally obligated to keep its two highest-profile players, quarterback Ryan Tannehill and running back Derrick Henry. Fans whose hearts were captured by Tannehill and Henry in December and January would be crushed if either (and especially Henry) were to get away. 

But while Tannehill was the league's highest-rated passer in 2019, the sample is relatively small. There's a much larger sample from his time with the Miami Dolphins that indicates he's a mediocre quarterback prone to catch fire at times. He posted a 129.9 passer rating during a three-game hot streak in 2018 and three 120-plus ratings during a five-game run to close out the 2016 season, but he was mediocre for much of his seven-year tenure in Miami. 

The Titans could easily regret committing more than $25 million a year to Tannehill ahead of his age-32 season. 

Meanwhile, Henry should be in line to command the biggest running back contract in the league following a dominant breakout season in which he led the NFL with 1,540 rushing yards and 16 rushing touchdowns. But cautionary tales like Le'Veon Bell, Todd Gurley and David Johnson should scare Titans general manager Jon Robinson. 

Nine running backs are making more than an average of $5 million per season, and none of those nine participated in the 2019 playoffs. Each Super Bowl team's top back was undrafted, and a team featuring the league's leading rusher hasn't won the Super Bowl this century. 

Throw in that Henry's aggressive style of play could lead to a short prime at a short-shelf-life position and it's easy to imagine the Titans having second thoughts about a blockbuster deal in the near future. 

Beyond that, they also have to take care of pillar right tackle Jack Conklin and veteran slot cornerback Logan Ryan. That'd leave them practically no room to improve elsewhere on the open market.

Los Angeles Chargers

The Los Angeles Chargers enter the season in good shape, cap-wise, with just short of $65 million in projected space. And while they have fewer big-name impending free agents on the roster, the fear with the Bolts is they're liable to act desperately (or foolishly) in a critical offseason. 

The Chargers are moving into the new SoFi Stadium, where they'll clearly be second fiddle to the more popular and successful Los Angeles Rams. They'll likely feel the need to make a splash to build hype ahead of that move, and that approach to free agency almost always comes back to bite you. 

Plus, general manager Tom Telesco has to know he's running out of rope. The Chargers have made the playoffs just twice since Telesco took over in 2013 (and only once in the last six seasons). They're better than their 5-11 record in 2019, but to make a legitimate playoff run for the first time in over a decade, they have a lot of work to do. 

Not only do they have to replace departed quarterback Philip Rivers, but the offensive line is a mess. Left tackle Russell Okung missed 10 games last year and will be 33 in 2020, right tackle Sam Tevi is a complete liability, 2017 draft picks Dan Feeney and Forrest Lamp haven't panned out at guard, and 30-year-old center Mike Pouncey is coming off a major neck injury. And it won't be easy to bolster that unit in free agency, because top-notch linemen rarely hit the market and are highly sought-after when they do. 

Additionally, running back Melvin Gordon III and tight end Hunter Henry both have expiring contracts, while Gordon's potential permanent replacement, Austin Ekeler, is scheduled to be a restricted free agent. 

The Chargers have to take a calm, cool and focused approach to free agency, but it's easy to see them caving under the pressure and acting recklessly instead. At least they'd have a chance to redeem themselves with the No. 6 overall pick in April's draft.