The 2018 edition of NFL free-agency frenzy is almost here.

With contract negotiations starting Monday and the signing period officially opening Wednesday at 4 p.m. ET, national NFL writers Kevin Seifert and Dan Graziano break down everything you need to know about the market -- including players primed for big paydays, others looking for prove-it deals and more.

Note: Age is listed based on how old each player will be at the start of the 2018 season.

Jump to: Top free agents by category | Salary cap highlights | Team needs

Salary cap highlights

Here are some notable cap numbers, according to ESPN's Roster Management System (as of March 12).

Teams with the most space

1. Cleveland Browns: $114,464,967

2. New York Jets: $90,935,706

3. Tampa Bay Buccaneers: $74,154,821

4. San Francisco 49ers: 73,176,957

5. Indianapolis Colts: $72,849,359

Teams with the least space

1. Philadelphia Eagles: minus-$8,685,978

3. Miami Dolphins: minus-$7,970,304

3. Kansas City Chiefs: minus-$3,871,249

4. Pittsburgh Steelers: $1,204,886

5. Dallas Cowboys: $1,653,641

Top overall free agents

1. Kirk Cousins, QB

2. Drew Brees, QB*

3. Case Keenum, QB*

4. Andrew Norwell, G*

5. Jimmy Graham, TE

6. Sheldon Richardson, DT

7. Nate Solder, OT

8. Trumaine Johnson, CB

9. Star Lotulelei, DT*

10. Allen Robinson, WR*

*Free agents who ESPN has confirmed intend to sign with specific teams when free agency officially opens on Wednesday.

See the full ranking of the top 100 free agents.

Free agents most likely to break the bank

Kirk Cousins, QB

2017 team: Redskins | Age: 30

We don't have much precedent for this situation: An upper-level quarterback available on the open market in the prime of his career. Cousins will get at least one offer that would make him the NFL's highest-paid player, at least for now, and could approach an average of $30 million annually. -- Seifert

Drew Brees, QB

2017 team: Saints | Age: 39

Brees has the Saints in a tough spot. They couldn't use the franchise tag, per the terms of his expiring contract, and would have an $18 million salary-cap acceleration if they don't sign him by March 14. If he wants, Brees could push for a deal that at least matches his current $24.3 million annual average, a nice sum for a player coming up on 40. -- Seifert

Andrew Norwell, G

2017 team: Panthers | Age: 26

If you're skeptical about what a guard can get on the open market, recall the deal Kevin Zeitler received last year from the Browns: five years, $60 million, with $31.5 million guaranteed. And Norwell, unlike Zeitler, was a first-team All-Pro in his contract year. -- Seifert

Nate Solder, OT

2017 team: Patriots | Age: 30

Reasonable people can debate whether Solder is an upper-tier player, but no one can argue the value of even a competent left tackle in free agency. In 2017, the Rams gave Andrew Whitworth -- at age 35 -- a deal that averaged $11.25 million per year. Solder could cash in if he decides to leave the Patriots. -- Seifert

Trumaine Johnson, CB

2017 team: Rams | Age: 28

After two years on the Rams' franchise tag, Johnson finally has the opportunity to hit the market. He'll be arguably the best cover corner available, which means a big payday, even if he has never made a Pro Bowl. -- Seifert

Potential value signings

Teddy Bridgewater, QB

2017 team: Vikings | Age: 25

A two-season layoff following an August 2016 knee injury naturally depresses Bridgewater's value. But in a best-case scenario, a team could acquire a quarterback who -- after knocking the rust off -- could start for 10 seasons or more. At the very least, Bridgewater will bring supreme professionalism and attitude to any role he receives. -- Seifert

Preston Brown, LB

2017 team: Bills | Age: 25

Teams don't step out much for linebackers unless they are also pass-rushers, but Brown can make a big difference relative to what he is likely to be paid. He's a tackling machine (512 in four seasons) who hasn't missed a game in the NFL. -- Seifert

Jerick McKinnon, RB

2017 team: Vikings | Age: 26

Veteran running backs are usually bargains on the open market, considering their short shelf life. But whoever signs McKinnon will get a player who fits well into today's incarnation of NFL running backs. He is equally fluent in the running and passing games, and offers value as a returner as well. -- Seifert

Albert Wilson, WR

2017 team: Chiefs | Age: 26

At 5-foot-9, Wilson isn't the classic big receiver who typically finds big paydays. But in today's spread-oriented schemes, he can eat up a lot of yards between the 20s. -- Seifert

Anthony Hitchens, LB

2017 team: Cowboys | Age: 26

The Cowboys love Hitchens, even if you've never heard of him. He could be of value elsewhere, too. He can play inside or outside, at least in a 4-3 base scheme, and has missed only four games in his four-year career. -- Seifert

Most likely to get one-year, prove-it deals

Malcolm Butler, CB

2017 team: Patriots | Age: 28

Butler entered free agency in a weird spot following his mysterious Super Bowl benching, and the buzz in Indy was that he wouldn't find the deal of his dreams in free agency. I could see him taking a one-year deal for $9 million or so plus incentives, then hitting the market again in a year, perhaps under better circumstances. -- Graziano

Allen Robinson, WR

2017 team: Jaguars | Age: 25

His résumé makes him one of the top two wideouts on the market, but he's coming off a season lost to a Week 1 torn ACL. Robinson could find himself following the 2017 Alshon Jeffery model. Remember, Jeffery couldn't get the long-term deal he wanted on the market, so he signed with the Eagles for one year and $9 million plus incentives that could push the deal to $14 million. He got his extension from Philly late in the season, and obviously things worked out well there for everyone. -- Graziano

Sammy Watkins, WR

2017 team: Los Angeles Rams | Age: 25

Same case as Robinson, but probably at a higher number. Watkins didn't put up big numbers in the Rams' offense but is still viewed by many as a top talent. -- Graziano

Sam Bradford, QB

2017 team: Vikings | Age: 30

The leaguewide demand at quarterback could obviously lead to a long-term deal, but Bradford's knee is enough of a concern at this point that he might have to pick a spot (Arizona?) where he can prove himself healthy for a year before hitting the market again for one more big payday. -- Graziano

Tyler Eifert, TE

2017 team: Bengals | Age: 28

Injuries have defined his career so far, but when he has been on the field, he has shown himself to be a strong option in the red zone. The tight end market should be interesting, and a lot of teams are looking, but Eifert has a lot to prove before he can get his long-term deal. -- Graziano

Might not sign until after initial surge

Paul Richardson, WR

2017 team: Seahawks | Age: 26

Richardson will hold some appeal as a speed threat who is still young, and teams can talk themselves into the notion that he didn't reach his potential in a Seattle offense in which protection issues prevented receivers from getting deep. Look for him to sign something similar to the five-year, $34 million contract Robert Woods got from the Rams last year -- and for the signing team to hope it gets anything like the deal L.A. got on Woods. -- Graziano

Patrick Robinson, CB

2017 team: Eagles | Age: 30

The Eagles are still working on trying to re-sign Robinson, but he might want to parlay his surprise big season into a trip to the free-agent market. If he does, he'll wait for the bigger names to sign their eight-figure-a-year deals, then pitch himself as a solid nickel option for a team looking to spend $5 million or $6 million per season. -- Graziano

Josh McCown, QB

2017 team: Jets | Age: 39

After a surprisingly strong season with the Jets, McCown should find work as a veteran bridge quarterback for a team looking to draft a guy and groom him. So McCown's market will be the teams that lose out on Cousins, Case Keenum, et al. -- Graziano

Bashaud Breeland, CB

2017 team: Washington | Age: 26

Breeland's name wasn't generating all that much buzz at the combine in Indianapolis, and it's still possible he ends up back in Washington if no team is willing to pay him $10 million or more per season. -- Graziano

Eric Reid, S

2017 team: 49ers | Age: 26

The safety market is a little bit flooded, and while Reid will be one of the better players on it, there's a fear -- which he shares, by the way -- that his role in the 2017 national anthem controversy could steer some teams away. -- Graziano

Free agents who need the right situation

Case Keenum, QB

2017 team: Vikings | Age: 30

It is no coincidence that Keenum had by far his best season with by far the best team he has ever played for. His 69.7 Total QBR was the NFL's second best, but it's worth noting that after five years of inconsistency, Keenum broke through with help from an elite defense, one of the league's best playcallers (Pat Shurmur) and a diverse group of pass-catchers. -- Seifert

Dion Lewis, RB

2017 team: Patriots | Age: 27

Lewis is at his best when used in multiple roles. More and more teams have the capacity to roll their backs through the backfield, into the slot and even to outside receiver positions. Some do not. Lewis needs a team that would use his complete skill set rather than box him in as a classic tailback. -- Seifert

Muhammad Wilkerson, DL

2017 team: Jets | Age: 28

Wilkerson's talent is undeniable, as are the disciplinary issues he had in recent years under coach Todd Bowles. Wilkerson needs a franchise that can give him the right proportions of breathing room and structure. -- Seifert

Kenny Vaccaro, S

2017 team: Saints | Age: 27

Is he a safety? A linebacker? A hybrid? Vaccaro's next team would be best advised to have a specific, unique role in mind for his talents and limitations. -- Seifert

Taylor Gabriel, WR

2017 team: Falcons | Age: 27

At 5-foot-8, there are some things Gabriel can't do. But we've seen at various points in his career -- especially in 2016 with the Falcons -- how his unique open-field skills can be utilized. The less conventional his role, the better. -- Seifert

Most likely to make a big immediate impact

Jimmy Graham, TE

2017 team: Seahawks | Age: 31

Although he might not be as explosive as he once was, Graham is still exceptionally difficult to defend in the red zone. Last season, his 10 touchdown receptions (on only 95 targets) were tied for No. 2 in the league. Graham would immediately enhance a team's scoring efficiency. -- Seifert

Ryan Jensen, C

2017 team: Ravens | Age: 27

The most efficient way to improve an offensive line is to upgrade at left tackle and/or center. At the moment, Jensen is the best center available on the market. -- Seifert

NaVorro Bowman, LB

2017 team: Raiders | Age: 30

Injuries have been an issue over the past three seasons, but when he got healthy last season, Bowman made an immediate impact on the Raiders' run defense. -- Seifert

Donte Moncrief, WR

2017 team: Colts | Age: 25

Moncrief was an explosive weapon when Colts quarterback Andrew Luck was healthy. Pair him with a good downfield thrower and look out. -- Seifert

Rashaan Melvin, CB

2017 team: Colts | Age: 28

A 6-foot-2 cornerback can help shift a defense's schemes -- assuming Melvin covers the way he did last season for the Colts. -- Seifert

More top guys likely to sign with new teams

Sheldon Richardson, DT

2017 team: Seahawks | Age: 27

The defensive overhaul is in full swing in Seattle, and it's hard to believe it will break the bank for Richardson after just one year. Expect him to do quite well on the market as a defensive lineman who has shown disruptive ability in 3-4 and 4-3 defensive fronts. -- Graziano

Dontari Poe, DT

2017 team: Falcons | Age: 28

The Falcons would like Poe back, but they got him on a bargain deal last year, and he did well enough there that he should be able to spin it into a two-or three-year deal worth $10 million or $11 million per season. -- Graziano

Trey Burton, TE

2017 team: Eagles | Age: 26

A tight end who threw a memorable touchdown pass in the Eagles' Super Bowl victory, Burton is a versatile talent who isn't likely to fit under Philadelphia's salary cap. He'll be a bigger part of the offense in his next stop. -- Graziano

AJ McCarron, QB

2017 team: Bengals | Age: 27

As soon as McCarron won the grievance that made him an unrestricted free agent, he was gone from Cincinnati. McCarron will look for a place he can be the starter after years as Andy Dalton's backup. Watch Cleveland and Arizona as potential landing spots. -- Graziano

Terrelle Pryor Sr., WR

2017 team: Washington | Age: 29

Yeah, no, that didn't work. Washington was Pryor's landing spot last year when he couldn't get the long-term deal he sought. He took a one-year deal with incentives and didn't do much to hit them, and Washington will surely move on. Expect Pryor to need another one-year job in the hopes of rekindling what he had in Cleveland two years ago. Heck, maybe he does it in Cleveland. -- Graziano

Bonus: Sneaky trade candidates

Jarvis Landry, WR

Current team: Dolphins | Age: 25

Not sure how "sneaky" this is, since at this point it seems everyone knows the Dolphins are trying to trade their franchise player. Chicago, Baltimore, San Francisco and Tennessee are teams to watch. -- Graziano

Earl Thomas, S

Current team: Seahawks | Age: 29

Seattle won't give Thomas away, and I still think the team is more likely to extend him than to let him go. But if someone is willing to pay a high enough price, Thomas might not get to stick around for the defensive rebuild. -- Graziano

Cordy Glenn, OT

Current team: Bills | Age: 28

Glenn has been on the market since last October, when Buffalo couldn't find a taker at its price. There aren't many top tackles on the market, and it's not a great draft for tackles. Expect the Bills to find a match for Glenn this offseason. -- Graziano

Martavis Bryant, WR

Current team: Steelers | Age: 26

The Steelers can say all they want about not wanting to trade Bryant, but he still wants to go to a place where he can be the No. 1 wide receiver. Once the free-agent market shakes out, some team will offer more than they have so far. -- Graziano

Ereck Flowers, OT

2017 team: Giants | Age: 24

The Giants need a major shake-up on the offensive line, and they're going to get one. Likely to lose guard Justin Pugh and center Weston Richburg in free agency, they also could look to part ways with former first-round pick Flowers. As is the case with Glenn in Buffalo, the potential return could improve as teams confront the scarcity of options on the market. -- Graziano

Offseason needs for all 32 teams

Here are the areas of need for all 32 teams as compiled by ESPN Stats & Information (as of the start of free agency).

AFC East

Buffalo Bills: WR, DT, DE

Miami Dolphins: OL, LB/S, impact players

New England Patriots: DL, DE/LB, CB, OT

New York Jets: QB, DL, G/C

AFC North

Baltimore Ravens: WR, TE, LB/S

Cincinnati Bengals: OL, LB, TE

Cleveland Browns: QB, WR, DL

Pittsburgh Steelers: LB, S, DT

AFC South

Houston Texans: OL/OT, TE, DB

Indianapolis Colts: pass rush, DB, OL, RB

Jacksonville Jaguars: WR, TE, OL, slot CB

Tennessee Titans: ILB, CB, G

AFC West

Denver Broncos: QB, OL, LB/S

Kansas City Chiefs: CB/slot CB, ILB, WR

Los Angeles Chargers: LB, DT, G

Oakland Raiders: CB, S, OL

NFC East

Dallas Cowboys: DL, TE, WR

New York Giants: OL, RB, LB

Philadelphia Eagles: LB, OL, DB

Washington Redskins: DL/LB, OL, CB

NFC North

Chicago Bears: WR, CB, OL

Detroit Lions: defense, RB, TE

Green Bay Packers: TE, CB, OLB

Minnesota Vikings: QB, OL, DL

NFC South

Atlanta Falcons: DT, DE, TE, G

Carolina Panthers: WR, slot CB, DE, G/C

New Orleans Saints: TE, DE, CB

Tampa Bay Buccaneers: DB, pass rush, RB, OL

NFC West

Arizona Cardinals: QB, WR, OL

Los Angeles Rams: rush D, OL, DB

San Francisco 49ers: CB, WR, OL

Seattle Seahawks: RB, OL, DB, TE