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Every team in the NFL wants to play physical man coverage. Jam the receivers, impact the release and funnel the routes inside. Go ahead and attack the wideouts at the snap, slide the feet and then drive to the hip to squeeze these guys to your help in the middle of the field.

That’s how you dictate the flow of the game from a defensive perspective.

However, to play true man coverage in this league, you need a legit free safety—an angel over the top—who can close the seam and the post because of his range, instincts and transition speed to break on the ball.

That’s why Devin McCourty is going to get paid big money on Tuesday when he hits the open market at the start of free agency.

These guys are hard to find. I’m talking about the top-tier free safeties who allow NFL teams to consistently play single-high schemes while shutting down the middle of the field.

McCourty might not have the same skill set as Earl Thomas. He's a rare talent. The Seahawks free safety is a top-five player on the defensive side of the ball in the NFL. But in terms of overall value to a defensive system, yeah, it’s pretty close in my opinion when comparing Thomas and McCourty.

All you have to do is look at the Patriots' tape from this past season and focus on the Cover 1 (man-free) and Cover 3 (three-deep, four-under zone) schemes Bill Belichick’s defense leaned on during New England’s run to a Super Bowl title.

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Sure, the Patriots had talent at the cornerback position with Darrelle Revis, Brandon Browner, etc.—defensive backs who can play press-man. And no one can forget Malcolm Butler’s play to wrap up the Super Bowl victory when he intercepted the slant route versus Russell Wilson and Seattle in the final seconds down in Arizona. That was clinic tape technique from the rookie on the game’s biggest stage.

However, without McCourty over the top and getting enough depth to drive top-down on the seam, post or dig (square-in), that defense just doesn’t produce the same high-level results in 2014.

McCourty has the ability to roll down in coverage, and his footwork is reflective of his time playing cornerback earlier in his career. He glides in his pedal and displays the quick plant and drive (transition) to break on the ball when playing from an off-man position. McCourty can also work from the deep half (Cover 2) or drop underneath as a “robber” to play the inside hole.

But his true value, the money-making value he is going to see in free agency, comes from his ability to patrol the deep middle.

Here’s an example of what I’m talking about from the All-22 tape with the Patriots playing Cover 1 and McCourty in the middle of the field.

Credit: NFL Game Rewind

This is what every defensive back coach wants to see on the film with the free safety gaining depth, keeping his shoulders square to the quarterback and putting himself in a position to break on the throw. This allows McCourty to drive top-down on the dig, jump the seam, take away the post and overlap the 9 (fade) route (get to two yards outside of the numbers).

Plus, McCourty has rare instincts at the position that always show up on the tape.

This is why McCourty can play fast (game speed), cover a lot of ground and create clean, positive angles to the football. He is an extremely smart and tough player who anticipates route concepts based on formation, alignment, splits and the initial wide receiver stem (or release).

That allows McCourty to break early on the ball or create a downhill, 45-degree angle to the point of attack while also showing the flexibility to flip his hips in the deep middle.

During the Patriots’ divisional playoff win over the Ravens, McCourty made one of the best reads all season from the middle of the field that produced an interception versus Joe Flacco on a deep crossing route. Check out the GIF below:

Credit: NFL Game Rewind

The Ravens are trying to occupy McCourty with the clear-out seam to create a throwing window to target the deep over or deep crossing route. However, McCourty stays square in his pedal, reads the eyes of the quarterback and breaks on the ball—before the throw.

McCourty can now create that downhill angle to the ball we just talked about while cutting off the receiver at the point of attack. The idea here is to identify the route, read the shoulders of the quarterback and go make a play.

Take one more look at this interception from the end-zone angle to see McCourty finish on the ball. This is a perfect example of a free safety jumping a route while protecting the top of the secondary.

Credit: NFL Game Rewind

What is McCourty’s value on the open market? Considering that Thomas signed a four-year contract worth $40 million, McCourty can sign a deal around $8 million on average. And the price could go up considering how many teams are desperate to upgrade the safety position with a true middle-of-the-field defender.

McCourty could re-sign with the Patriots and stay in New England. That’s a real possibility. But let’s also look at the Eagles, Giants, Bears, Colts, Titans, Jets or Falcons—teams that need to address the back end of the secondary.

The point here is that McCourty will have opportunities to cash out in free agency given the need at the position in the NFL and a very weak draft class coming in. Outside of Alabama’s Landon Collins—who I see earning his money as a strong safety in the league—this 2015 class lacks impact talent. Collins will go in the first round, but after that, we might not see a safety come off the board until late in the second round.

For teams that fail to land McCourty in free agency, the Broncos’ Rahim Moore would be a solid pickup as a second option on the market. At only 25 years old, Moore can step in and start for a lot of teams in the NFL. He has the range and ball skills to make plays over the top.

However, if I’m running one of those squads that wants to play man coverage and dictate from the secondary, McCourty is the No. 1 player on my list. He is the key to closing down the middle of the field. And that's why you pay big money for an impact player at free safety.

Seven-year NFL veteran Matt Bowen is an NFL National Lead Writer for Bleacher Report.

Follow @MattBowen41