Steve Dykes/Getty Images

The 2016 NFL free-agency period is less than one month away before franchises look to alter their future with major acquisitions. The free-for-all bidding officially begins March 9 at 4 p.m. ET, which leaves teams time to study potential targets. Despite the time spent planning, there are always free agents who become hidden gems from the lack of interest or proper homework on the players.

Los Angeles Rams cornerback Trumaine Johnson is likely to be the hidden gem of the 2016 free-agency class. The 26-year-old fourth-year cornerback from the University of Montana has grown leaps and bounds to become a quality starter. But he may be overlooked due to the quantity of quality cornerbacks available this offseason.

It’s rare for true No. 1 cornerbacks to ever see the unrestricted free-agent market. One of the best of all time, Darrelle Revis, cashed in with a five-year, $70 million deal last offseason with the New York Jets. This year could bear multiple top cornerbacks as well.

It’s possible and maybe even likely the Carolina Panthers will franchise tag Josh Norman to keep him from seeing the open market. The Kansas City Chiefs may do the same with Sean Smith. Each is a legitimate top cover cornerback in the NFL right now and will command a top salary.

Right behind those two is a group of high-end No. 2 or low-end No. 1 cornerbacks. Johnson is the one who stands out the most from the likes of teammate Janoris Jenkins, Green Bay Packers cornerback Casey Hayward and New York Giants corner Prince Amukamara. This isn’t just because Johnson is the tallest of the group at 6’2”, 205 pounds, either.

Video Play Button Videos you might like

The Rams may not be able to retain both Jenkins and Johnson, even though they’re projected to enter free agency with $31 million in cap space before veteran cuts, per Over the Cap. Jenkins is the better system fit for the Rams and may be cheaper since he is smaller and two years older than Johnson.

I took an eight-game sample for Johnson to see how he improved in coverage from 2014 to 2015. He posted a career-high seven interceptions in his first full season starting and is young enough to show improvement in the next two years. The results from my charting were highly encouraging that his arc hasn’t peaked yet.

The games I used for Johnson’s sample were the best eight receiving corps he faced in 2015: the Washington Redskins, Pittsburgh Steelers, Arizona Cardinals, Green Bay Packers, Minnesota Vikings, Detroit Lions, Tampa Bay Buccaneers and Seattle Seahawks in the season finale. You can read more about my methodology over at DraftCentric.

NFL Game Pass

The point of the table below is not just to see when Johnson was targeted or allowed a catch. Did he provide quality coverage and force a difficult throw or catch? That's more important question for me. And at what rate did he allow receivers to get open compared to his peers?

I charted 36 cornerbacks in 2014, and 20 in 2013. The project successfully predicted the success of Marcus Peters as a rookie, Stephon Gilmore, Bradley Roby and Jason Verrett. It also helped foresee relative struggles from Byron Maxwell and Joe Haden. These charts aren’t perfect, but they help show who the player is and where he can improve or be picked on.

After looking at the Rams defense and Johnson specifically, there’s no question he played much more confidently and technically sound. The Rams mostly ran off-man, Cover 2 and Cover 4 schemes, which allowed Johnson to be exposed to multiple strategies. Off-man was where he shined the most and made several of his highlight-reel interceptions.

NFL Game Pass

Off-man coverage allows a lengthy and somewhat linear player like Johnson to worry less about footwork off the line of scrimmage and more about the ball and receiver. Effective off-man coverage requires discipline, acceleration and good timing. It can be a mask for physically limited players who need the extra cushion to survive on the outside.

Johnson does not need to be hidden because of his physical traits, though. He has excellent length and knows how to use it effectively. He is one of the better defenders on both curl and go routes in the NFL because he doesn’t panic when the ball is arriving. His entire coverage process is smooth, and he finds the ball well.

Trumaine Johnson's Coverage Stats vs. 2014 NFL Averages Route Trumaine Johnson (2015) Coverage Score NFL Average Coverage Score Cross 0% 37.4% Quick In-Out 42.85% 32.2% Slant 33% 49.5% Comeback 50% 38.9% Curl 15.78% 24.7% Deep Out 50% 44.6% Dig 50% 40% Corner 50% 39.7% Post 42.85% 35.9% Go 13.63% 24.2% Cumulative 30.23% 32.5% DraftCentric

This is reflected in his 2015 coverage productivity chart above. Compared to his peers, Johnson does an above-average job of guarding the sideline. His coverage on curl routes and go routes was well below the league average in 2014 despite being heavily exposed to those two routes in particular.

This is also encouraging for potential suitors to look at because there’s reason to have faith Johnson will fit in other schemes. I’d go as far as to say Johnson will do even better in press-based schemes, whether it be in man or Cover 3 or Cover 4 zones. He has the ability to play trail coverage well, given his length and ball skills.

The Rams were playing schemes that fit their other personnel much better than Johnson’s skill set. Instead of a defense putting him in space and forcing him to make decisions, he’s capable of playing a multitude of coverages at a high level. This is where he may be a gem to a new team.

NFL Game Pass

There aren’t many examples of the Rams using Johnson in press coverage. His inexperience showed when he did try it against Detroit Lions receiver Calvin Johnson. But he did well against other physical presences such as Martavis Bryant and Michael Floyd in their individual matchups.

The lack of scheme versatility is one reason why Maxwell struggled to impress in his first season away from Seattle. Expectations were sky-high last year after he signed a six-year, $63 million deal. But his coverage chart showed particular weakness against routes requiring foot precision and quickness such as slants and curls. He needed the comfortable confines of Seattle’s scheme to protect his weaknesses.

Johnson doesn’t have that same limitation. While every team uses a variation of coverages, some are more extreme with their coverage patterns than others. Defensive coordinators who want to throw a multitude of different looks would appreciate Johnson’s ability to switch as needed.

His overall coverage score of 30.23 percent is just outside of the sub-30 percent club. That is where I say a cornerback is comfortably a viable No. 1 option. The elites get beaten no more than 25 percent of the time, and the chasm between the three tiers is considerable.

NFL Game Pass

A major positive for Johnson is his interceptions. While some cornerbacks are great at smothering receivers, they do not force turnovers. Johnson has good hands and routinely locates the ball. The ability to force a turnover can make up significantly for more coverage lapses.

There is legitimate hope for improvement considering Johnson’s youth. He’s started just 33 games in his four-year career and responded well after earning the starting job in late 2014.

His injury history has caused him to miss nine games in the last two years. That’s something teams will need to factor into their contract negotiations. But he is worth a potentially major investment based on the market.

Massive spending is coming this offseason with so much talent and money available. High-quality cornerbacks are rarely available, so expect Johnson and the rest of the free-agent cornerbacks to cash in. A Maxwell-like deal makes sense in terms of cost per year.

The best suitors for Johnson will have a good pass rush, strong defensive coaching and a history of mixing off-man and vertical zone-coverage patterns. The Oakland Raiders, Jacksonville Jaguars and Cincinnati Bengals are the best fits for Johnson if the Rams do not tag him.

All stats used are from Pro-Football-Reference.com.

Ian Wharton is an NFL Featured Columnist for Bleacher Report.

Follow @NFLFilmStudy