Please Don't Go: NFL Players Who Must Be Re-Signed in 2020 Free Agency

Next year's edition of NFL free agency doesn't kick off until March 18, but teams are undoubtedly already planning their strategies. The first step is determining which players should be re-signed.

This can be a challenge, both because of the salary cap and because of the pending free-agent market. Overspending to keep one player could result in a failure to upgrade another position. At the same time, some players are too important to let go.

Those are the ones we'll examine today. Based on their importance to their respective teams in 2019 and factors like age and team fit, these players absolutely must be re-signed before they hit the open market.

We won't cover starting quarterbacks since, in most cases, re-signing a good one is an obvious choice.

The Seattle Seahawks traded for defensive end Jadeveon Clowney just before the start of the 2019 season. Re-signing him would help Seattle get the most out of its investment, but that's not why the Seahawks should do so.

Now that Clowney is rounding into form in Seattle, he's becoming a game-wrecker. If you watched him against the San Francisco 49ers in Week 10, you witnessed his ability to take over a game. Even when Clowney doesn't get to the quarterback, he's often able to generate pressure or get into passing lanes.

He has 25 tackles, three sacks, three passes defended, an interception, two defensive touchdowns and three forced fumbles this season. If the Seahawks are going to go on a playoff run, he'll likely be a big reason why.

Clowney is a difference-maker who opposing teams must game-plan for, and he's just entering his prime at 26 years old. He's an asset Seattle needs to keep.

Though he's now in his eighth season with the Houston Texans, linebacker Whitney Mercilus has long been overshadowed by pass-rushers Clowney and J.J. Watt.

"I was like, 'Who is Whitney Mercilus? This guy is unbelievable,'" Jacksonville Jaguars head coach Doug Marrone told reporters in Week 9 of his first impression of Mercilus in 2015.

With Clowney in Seattle and Watt on injured reserve, Mercilus is Houston's most disruptive defender. He has 32 tackles, 5.5 sacks, an interception and four forced fumbles. This isn't the first year in which he has been a star either.

Though he has never been to a Pro Bowl, Mercilus has been one of Houston's biggest defensive assets since joining the team as a first-round pick in 2012. He averaged 7.5 sacks over his first five seasons with the franchise, and he should match or exceed that total in 2019.

At 29 years old, Mercilus should have several strong seasons ahead. The Texans must re-sign him—especially with Watt's future uncertain because of yet another season-ending injury.

At 32 years old, New England Patriots safety Devin McCourty isn't as young as most players on this list, but there might not be a guy more important to his team.

Fast, physical, sticky in coverage and possessing a high football IQ, McCourty is the centerpiece of New England's impressive secondary. He adds a ton of versatility to the back end of the defense and remains one of the biggest reasons why the Patriots can afford to lean on man coverage with their cornerbacks.

When a corner like Stephon Gilmore slips up in coverage—which is admittedly rare—McCourty is in position to make a play more often than not. He's also one of the most vocal leaders on the roster.

"Players circle around him right before kickoff to hear his words of wisdom, and he delivers them forcefully and passionately," Karen Guregian of the Boston Herald wrote.

New England's defense wouldn't be the same without McCourty, which is why he's the team's most important pending free agent next to Tom Brady.

The 49ers lost their first game of the season in Week 10. While an overtime loss to Seattle won't make anyone question San Francisco's championship aspirations, one thing was clear: The 49ers offense missed Emmanuel Sanders and George Kittle.

According to NFL Media's Andrew Siciliano, quarterback Jimmy Garoppolo was just 3-of-18 on passes longer than 10 yards with an interception against Seattle. That's the worst rate this season by any quarterback with at least 15 such throws in a game. With Sanders—who left the game early because of injury—and Kittle in the lineup, Garoppolo probably doesn't struggle as much.

Sanders will be a free agent in the spring.

Acquired a week before the trade deadline, he immediately made an impact on San Francisco's offense. In a little over two games, he has 13 receptions for 161 yards and two touchdowns.

While Sanders is 32 years old, he's still a quality deep threat, and his veteran savvy can help out an inexperienced quarterback like Garoppolo. Keeping him will be vital, not only for the offense's success but also for Garoppolo's growth.

Keeping Sanders will be important for San Francisco's offense. Keeping defensive lineman Arik Armstead will be equally important for its defense.

While the 49ers are deep along the defensive line, Armstead isn't a player they can afford to let go. He's a valuable edge-setter against the run and has enough of a pass-rushing presence that San Francisco doesn't have to take him off the field in passing situations. He's also capable of kicking inside to make room for guys like rookie edge-rusher Nick Bosa.

No, he isn't as relentless as Bosa, but Armstead's seven sacks this season haven't come by accident.

"Armstead, in his fifth season, has turned into a dominant force both as a run defender on first and second downs and as a pass-rusher working on the interior in nickel situations," Matt Maiocco of NBC Sports Bay Area wrote.

The 49ers defense has enough talent to survive without Armstead, but losing him would cost defensive coordinator Robert Saleh a ton of versatility up front.

When quarterback Jacoby Brissett has been healthy this season, the Indianapolis Colts have been dangerous. They've gone 5-2 in games he's started and finished, and there's little reason to think Indianapolis cannot have long-term success with Brissett under center.

Keeping left tackle Anthony Castonzo would go a long way toward ensuring it.

Though he is 31 years old, Castonzo is playing at a terrific level. He's committed just one penalty and allowed two sacks, according to Pro Football Focus. Indianapolis ranks sixth in adjusted line yards when running behind the left tackle, according to Football Outsiders.

Most important is the fact that the Colts offensive line has shown both growth and consistency over the last two seasons—and Castonzo has been a big part of that.

He won't be cheap, and other areas will need to be addressed in free agency and the draft. However, losing him would create a massive hole on the line that would be difficult to plug.

Outside linebacker Shaquil Barrett is having a breakout year with the Tampa Bay Buccaneers. After amassing 14.0 sacks in five previous seasons, he's leading the NFL with 11.5 after 10 weeks. More than an edge-rusher, Barrett has added 31 tackles, an interception and four forced fumbles.

The possibility exists that he will be a one-year wonder. However, the Buccaneers need to re-sign him and give him the opportunity to prove otherwise. If he is developing into an elite defender, the Bucs will kick themselves for letting him walk at just 27 years old.

Barrett is entering his prime. Combined with a transition to Todd Bowles' defense, that could be responsible for his breakout.

Using the franchise tag may be the best tactic, as it will give Tampa another year to evaluate him before offering a long-term deal. It's an expensive option, but the Buccaneers are projected to have the third-most cap space of any team in 2020, according to Spotrac. Using the tag on their biggest defensive difference-maker is worth it.

The Dallas Cowboys obviously want to extend starting quarterback Dak Prescott. To ensure he succeeds moving forward, however, Dallas absolutely must re-sign wide receiver Amari Cooper. Prescott and the entire Cowboys passing attack benefits from his presence on the field.

As pointed out by Jared Dubin of CBS Sports, Prescott is a different quarterback with Cooper in the lineup. Before the wideout's arrival in the middle of last season, Prescott had completed 64.7 percent of his career passes and held a passer rating of 94.0. His completion percentage and passer rating have jumped to 69.8 and 102.7, respectively, in games played with Cooper.

Running back Ezekiel Elliott is still the centerpiece of the Cowboys offense. However, Cooper is a close second. Opposing defenses must account for him, and he opens up a lot for fellow pass-catchers Michael Gallup, Randall Cobb and Jason Witten.

Prescott is not the only one to benefit from playing alongside him.

Teams rarely let No. 1 receivers walk, but keeping Cooper is especially important for the Cowboys and their ascending passing game.