The NFL's Biggest Under-the-Radar Free Agents Who Can Make Waves in 2020

Believe it or not, Tom Brady isn't the NFL's only impending free agent. 

In fact, more than 500 players are slated to officially hit the open market Wednesday. And while the majority of the focus right now is on Brady, Philip Rivers, Derrick Henry, Amari Cooper, Jadeveon Clowney and a few other big names, several lower-tier free agents will inevitably make larger impacts than expected in 2020 and beyond. 

Here's a look at nine under-the-radar breakout candidates slated to hit the free-agent market. 

Marcus Mariota likely won't land a starting job in free agency, but the 2015 No. 2 overall pick will likely sign with a team that doesn't feel overly confident in its starting quarterback. And if that starter shows signs of weakness, Mariota will quickly become the most popular man in town. 

Eventually, he'll likely get one more chance to prove he isn't a bust after a disappointing five-year tenure with the Tennessee Titans. And with less pressure this time around, it's entirely possible he'll actually come through. 

There's little doubt Mariota has the talent, and it's not as though his career numbers are disastrous. His career passer rating is just a couple points lower than Jared Goff's, all of his rate-based numbers are superior to Cam Newton's dating back to 2015, and Ben Roethlisberger, Ryan Tannehill and Rivers all have higher interception rates. 

He's only 26, and it's not hard to imagine him flourishing in a new environment and a new decade.  

At his position and with his limited resume, running back C.J. Prosise likely won't command more than the minimum salary on the free-agent market. But the 2016 third-round pick still has potential. 

Prosise averaged 5.7 yards per carry as a rookie. Unfortunately, each of his next three seasons was derailed by an injury that forced him to IR. He's carried the ball just 35 times since that rookie campaign, but he's still only 25 years old. 

If he can stay healthy in the right environment, a player with his talent and versatility could explode. But at the very least, a healthy Prosise could work as an ideal pass-catching complement to a prototypical back in some team's offense. 

You might be better off investing in that potential than paying close to top dollar for somebody like Melvin Gordon III or Kenyan Drake. 

Like Mariota, Breshad Perriman is widely viewed as a bust after he was selected in the first round of the 2015 draft. After lasting just three years with the Baltimore Ravens, one of which was lost to injury, he's essentially become a journeyman. 

But the 26-year-old wide receiver quietly performed well with the Tampa Bay Buccaneers in 2019, putting up a career-high 645 yards and six touchdowns. And what's most promising is that he finished that campaign with three consecutive 100-yard games. Five of his six touchdowns came in December. 

We know Perriman has top-notch playmaking ability. In fact, only five receivers with at least 150 targets since 2016 have higher yards-per-catch averages during that span. But he's always lacked consistency and durability at the NFL level.

That might be changing, which could give some team the chance to execute a coup by bringing him in for a lot cheaper than guys like Amari Cooper, A.J. Green and Robby Anderson. 

In 2017, Daryl Williams was one of the best right tackles in the NFL.

A serious knee injury cost him pretty much all of his 2018 campaign with the Carolina Panthers, and he wasn't as effective after returning in 2019. But the 2015 fourth-round pick is a great run-blocker with tremendous versatility and plenty of upside at the age of 27. 

Williams played every position along the Carolina line except center last season, and it's easy to envision him landing a starting job at any of those spots this offseason. But because he's coming off a so-so campaign preceded by a major injury, he's getting a lot less publicity than fellow impending free-agent offensive linemen Andrew Whitworth, Jack Conklin, Bryan Bulaga, Jason Peters, Brandon Scherff and Joe Thuney. 

He'll also likely get less money. But don't be surprised if the talented, accomplished and disciplined Oklahoma product really takes off at his next stop. 

It feels as though Carl Nassib is eventually going to explode. 

Unfortunately for the 26-year-old pass-rusher, that didn't happen while he was on his rookie contract. And that means he'll come cheaper than a lot of other impending free-agent edge-defenders next week.

But the 2016 third-round pick still recorded 12.5 sacks, 25 quarterback hits, 20 tackles for loss and three forced fumbles over the last two seasons as a part-time player for the Tampa Bay Buccaneers. He has the ability to take off in a larger role and the right environment. 

Unable to afford Jadeveon Clowney, Shaquil Barrett, Arik Armstead and Bud Dupree? Give Nassib a shot. You'll likely be pleasantly surprised. 

Andrew Billings isn't even the most popular defensive tackle on the Cincinnati Bengals roster. 

For the last few years, the highly accomplished Geno Atkins has overshadowed the young Billings, but that could help save some team serious cash on a talented interior defensive lineman with plenty of growth potential. 

The 2016 fourth-round pick's career statistics (80 tackles, 3.5 sacks, 12 quarterback hits) don't stand out, but he's a massive run-stuffer who takes up a ton of space and has plenty of tread on his tires after an injury and a general lack of playing time limited his wear and tear in 2016 and 2017. And he only turned 25 on March 6.

So while Chris Jones and D.J. Reader hog most of the attention on the free-agent market at the position, Billings could be a steal. 

Nick Kwiatkoski might never become a full-blown star, but the 26-year-old Chicago Bears linebacker hasn't missed a game since 2017 and is coming off his best season yet despite playing less than half of the team's defensive snaps. 

Few free-agent conversations include his name because he's an off-ball linebacker who has never been an every-down player, but the 2016 fourth-round pick could break out right after somebody buys his stock low. As Pro Football Focus' Ben Linsey wrote in February:  

"He doesn't have a season of full-time work under his belt yet, but in his two most recent seasons as a partial starter (2017 and 2019), Kwiatkoski has earned overall grades of 80.5 and 72.6 with well-rounded efforts across run defense, tackling, pass-rushing and in coverage. Those numbers came on 382 snaps and 512 snaps, respectively, so it remains to be seen how he handles a full season with a starter's workload. However, Kwiatkoski has shown enough to be intrigued by what he would look like in that role."

If Cory Littleton and Joe Schobert are too expensive, Kwiatkoski is your man. 

Brian Poole isn't a shutdown outside cornerback like Byron Jones, and he isn't a highly decorated slot corner like Chris Harris Jr.

But though the New York Jets' slot specialist isn't getting as much attention as those two headliners, he was actually PFF's highest-graded slot cover man in 2019. 

It was a breakout year for a player who was good but never great or consistent during his first three seasons with the Atlanta Falcons. But he found a groove in Gregg Williams' system, and as a 27-year-old with just 31 career starts under his belt, there's a lot of room for continued growth in New York or elsewhere. 

Poole will still cash in this month, but it wouldn't be surprising to see him settle for a one-year prove-it deal. And it would be less surprising to see him deliver with his first Pro Bowl campaign. 

Karl Joseph has a lot of talent and a lot to prove, which could be advantageous for whoever signs the thus-far-disappointing 2016 first-round pick of the then-Oakland Raiders. 

Joseph will come relatively cheap because he's fallen so far short of expectations, but he's done enough to barely avoid the bust label for now. He's started 41 games, his PFF grades have been decent, and he's a superb run defender in the box. 

A new setting might be just what the doctor ordered for a talented 26-year-old who could never quite put it together amid seemingly constant team-level acrimony in Oakland.

More support could go a long way.