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.

AFC EAST

Buffalo Bills

Fresh off an appearance in the AFC Championship Game, the Bills' future hasn't looked this bright since the 1990s. But with only three starters returning on the offensive line and a defense that lacks a consistent pass rush, general manager Brandon Beane will be busy fortifying the trenches.

Miami Dolphins

The Dolphins enter free agency focused on adding offensive talent to surround quarterback Tua Tagovailoa -- particularly reliable speed at wide receiver. Tampa Bay's Chris Godwin and Houston's Will Fuller are two potential fits.

New England Patriots

The Patriots have an abundance of salary-cap space in an offseason when many teams are feeling a crunch, so there's an opportunity for them to think big to fill glaring needs. Pass-catchers such as wideouts Chris Godwin, Allen Robinson II and Kenny Golladay and tight ends Hunter Henry and Jonnu Smith could be on New England's wish list. They also need to settle on a QB with Cam Newton a pending free agent.

New York Jets

With a projected $68 million in salary-cap space, the Jets are one of the few teams positioned to spend aggressively, even if that isn't the preference of general manager Joe Douglas. Cornerbacks Richard Sherman and Jason Verrett, who played for Jets head coach Robert Saleh in San Francisco, are names to watch in free agency.

AFC NORTH

Baltimore Ravens

The Ravens' focus this offseason is improving quarterback Lamar Jackson's supporting cast. A No. 1 wide receiver such as Allen Robinson or Kenny Golladay and a high-end interior lineman such as guard Joe Thuney or center Corey Linsley could be on their shopping list.

Cincinnati Bengals

If the Bengals can add another dynamic receiving target this offseason, their offense will be poised to take a big step in quarterback Joe Burrow's second season. The offensive line is another area of need. And if they don't bring back defensive end Carl Lawson, the Bengals will need to add another pass-rusher.

Cleveland Browns

With their offense in good shape, defense figures to be the focus for the Browns, who will look to surround pass-rusher Myles Garrett with more talent. Finding a playmaking linebacker and help for the secondary could be priorities in free agency.

Pittsburgh Steelers

Because of the smaller salary cap and their backloaded contracts, the Steelers don't have much money to use in free agency. The priority is to retain a few of their defensive players, such as cornerbacks Mike Hilton or Cameron Sutton, and find suitable replacements for wide receiver JuJu Smith-Schuster and running back James Conner. 

AFC SOUTH

Houston Texans

It's been a turbulent offseason for the Texans, with quarterback Deshaun Watson's future the biggest topic right now. Houston also must decide whether wide receiver Will Fuller is in its future plans. And granting J.J. Watt's request to be released means a big focus will be adding talent to the defense -- specifically the defensive line. 

Indianapolis Colts

The Colts addressed their quarterback situation with the addition of Carson Wentz, but there are other needs. The priorities include determining the future of wideout T.Y. Hilton, finding a replacement for left tackle Anthony Castonzo, adding help at linebacker and boosting the pass rush.

Jacksonville Jaguars

The Jaguars have the most cap space available ($77 million) in the league and needs at left tackle, tight end, defensive tackle and in the secondary. Potential targets in free agency are tight end Hunter Henry and defensive tackle Dalvin Tomlinson.

Tennessee Titans

After finishing 30th in the league with 19 sacks and allowing opposing offenses to score touchdowns on 69% of their red zone visits, the Titans need to improve their defense. Getting an outside linebacker via free agency is paramount.

AFC WEST

Denver Broncos

Denver's offseason might be defined by who stays, as safety Justin Simmons and defensive end Shelby Harris could hit the open market. The Broncos also have a significant decision to make on the option year for linebacker Von Miller, who missed last season because of injury.

Kansas City Chiefs

Addressing the offensive line will be a focus for the Chiefs, particularly with tackles Mitchell Schwartz and Eric Fisher coming off serious injuries. They also might be looking at help for the back seven on defense.

Las Vegas Raiders

For the Raiders, trying to find that elusive game-changing edge rusher while shoring up a young and riddled secondary should be priorities. A bruising, change-of-pace running back and an interior defensive lineman who can move the pocket are other potential targets.

Los Angeles Chargers

The Chargers could address their offensive line as they work to provide protection for quarterback Justin Herbert. They also need to secure another reliable wide receiver and decide what to do with tight end Hunter Henry, a pending free agent.