The 2021 NFL free-agency period officially begins at 4 p.m. ET on March 17, but speculation about which players might be switching teams this offseason began months ago.

With more than half of the league's 32 teams rumored to be considering a change at quarterback, with franchises dealing with a lower salary cap and with dozens of big-name players about to hit the market, this free-agency period promises to be one of the NFL's busiest in years.

With that in mind, ESPN's NFL Nation breaks down each team's needs and potential free-agent fits.

NFC EAST

Dallas Cowboys

While they will not be big spenders in free agency because of talks with quarterback Dak Prescott, the Cowboys have needs at all levels of the defense. The linebackers and cornerbacks could look much different next fall, and a pass-rusher could be a need if Aldon Smith doesn't return. 

New York Giants

Figuring out what to do with their defensive line is at the forefront of this offseason as the Giants decide whether they can afford to keep pass-rusher Leonard Williams and run-stuffer Dalvin Tomlinson. They also should be targeting top-of-the-market talent at edge rusher and wide receiver.

Philadelphia Eagles

The Eagles are projected to be more than $40 million over the 2021 salary cap and are in the midst of a youth movement, so it's unlikely they'll be major players in free agency. A veteran quarterback (Jacoby Brissett?), help at the skill positions and reinforcements for the secondary could be targets during the second wave of free agency. 

Washington Football Team

Washington must provide more help for its QBs, starting at the wide receiver and tackle positions. It also should have another tight end. Defensively, it needs a linebacker, safety and cornerback. A few receivers will tempt Washington because of their speed, including Curtis Samuel, Will Fuller and Nelson Agholor.

NFC NORTH

Chicago Bears

With little cap space and needs across the board, GM Ryan Pace will need to get creative to add a veteran QB and keep pending free agent Allen Robinson II at wide receiver. If the Bears are unable to land a big-name quarterback, veterans such as Alex Smith, Andy Dalton or Ryan Fitzpatrick could be within their price range. 

Detroit Lions

The Lions don't have much money after trading quarterback Matthew Stafford and aren't expected to contend immediately; GM Brad Holmes has made it clear he is going to build through the draft. However, big changes could be in store at wide receiver and along the defensive front seven with Kenny Golladay and Romeo Okwara in position to test the market. 

Green Bay Packers

The Packers have to decide whether they can afford to keep two members of their top-scoring offense: running back Aaron Jones and center Corey Linsley. There are signs GM Brian Gutekunst wants to add to the receiver group. And cornerback also could vault to the top of its needs if Green Bay doesn't re-sign Kevin King.

Minnesota Vikings

Coach Mike Zimmer said one of his priorities is to get more pass-rushers, after the Vikings notched a franchise-low 23 sacks last season. Melvin Ingram, Bud Dupree and Carl Lawson could be targets in free agency. The offensive line could be another focal point, as they need to upgrade their interior pass protection. 

NFC SOUTH

Atlanta Falcons

The Falcons have little cap space, but they could make a move for a running back such as James Conner or Leonard Fournette. Finding help for the pass rush and at cornerback could also be in the cards.

Carolina Panthers

Upgrading the quarterback position and rebuilding an offensive line that has only one starter under contract is the focus. Tight end is another need, and Hunter Henry could be a target in free agency.

New Orleans Saints

The Saints' budget will be constrained by the league's reduced salary cap. Safety Marcus Williams and defensive end Trey Hendrickson are pending free agents who should draw the greatest interest around the NFL. But quarterback Jameis Winston is probably the Saints' top priority, with Drew Brees expected to retire. 

Tampa Bay Buccaneers

The Buccaneers have an estimated $24 million in salary-cap space -- 13th most in the NFL -- and GM Jason Licht and coach Bruce Arians said the priority is re-signing their own. Wideouts Chris Godwin and Antonio Brown and linebackers Shaq Barrett and Lavonte David are among Tampa Bay's pending free agents. 

NFC WEST

Arizona Cardinals

The Cardinals made a big move on Monday by adding All-Pro J.J. Watt to a solid defensive line that already includes pass-rusher Chandler Jones. There are a handful of other positions such as wide receiver, cornerback and tight end that could help Arizona get over the hump and into the playoffs.

Los Angeles Rams

The Rams must find creative solutions in free agency, with three key defensive starters -- outside linebacker Leonard Floyd, safety John Johnson III and cornerback Troy Hill -- ready to test the market. Adding a deep threat for quarterback Matthew Stafford -- acquired in a trade that will become official at the start of the league year -- is a priority.

San Francisco 49ers

The 49ers have pressing needs in the secondary and on the offensive line, and they could be involved in the ever-evolving quarterback carousel, if the right opportunity arises. If left tackle Trent Williams leaves, the Niners could chase a pass-rusher such as Shaq Barrett or Yannick Ngakoue. 

Seattle Seahawks

With less than $10 million in cap space, the Seahawks have to free up money via cuts (Carlos Dunlap?), restructures (Bobby Wagner?) and maybe even a salary-shedding trade just to re-sign some of their own free agents, let alone add players.