Indianapolis Colts rookie linebacker Darius Leonard has had a terrific start to his career. Chicago Bears rookie linebacker Roquan Smith has a great career ahead of him. San Francisco 49ers rookie linebacker Fred Warner has played phenomenally at times this season.

However, the Cowboys' Leighton Vander Esch has been the best rookie linebacker in football through 10 weeks, and if the 2018 NFL draft happened today, he would be the first linebacker off the board.

Even though he was selected in the first round, no one thought Vander Esch's transition from Boise State to the NFL would be this easy, especially considering he missed large portions of offseason activities and training camp because of injuries.

It didn't matter. From the moment the Riggins, Idaho, native stepped on the field, he's exceeded expectations, playing, at times, better than perennial Pro Bowler and Cowboys captain Sean Lee. In fact, Vander Esch's play has led many to wonder whether Lee's time with Dallas (as a player) should come to an end as the veteran linebacker deals with yet another hamstring injury.

Without further ado, let's detail why Vander Esch has been the preeminent rookie linebacker in football by comparing his statistics to the others and detailing the traits that make him special:

Statistics

Stats courtesy of Pro Football Focus

Despite playing fewer snaps overall, Vander Esch still has more tackles than Smith and Warner and at least as many stops. Vander Esch also allows fewer yards per reception and yards-after-catch allowed per reception than either Smith or Warner.

Because Leonard has played 147 more snaps this season than Vander Esch, he has the advantage in the counting stats such as tackles and stops. But when you go by a per-snap basis, Vander Esch is much more productive, meaning if Leonard and Vander Esch played the same amount of snaps, Vander Esch's counting stats would exceed Leonard's.

Vander Esch has performed better in coverage than Leonard, allowing fewer yards per reception and YAC per reception.

*Note: Pro Football Focus defines a stop as a "win" for the defense or conversely a "loss" for the offense. PFF describes a "stop" further as an offensive gain on first down that is kept to less than 40 percent of the line to gain, less than 50 percent of the line to gain on second down and any third- or fourth-down play kept without a first down or touchdown.

Sideline-to-sideline playmaker

It's extremely unusual to see a 6-foot-4, 256-pound linebacker have the range Vander Esch has. Most linebackers blessed with that kind of size are almost always downhill thumpers who struggle to make plays outside the box. Vander Esch is a unicorn in the fact that he has all the size and skills of a downhill thumper, but also has the athleticism and range to make plays from sideline to sideline. Here's an example:

The touch pass has been one of the most difficult concepts to stop near the goal line this season. Most teams lack the second-level defender who can A) read and diagnose the touch pass quickly and B) have the athleticism to get to the ball carrier before he gets to the end zone.

Fortunately for the Cowboys, they have Vander Esch, who does a masterful job of sniffing out the touch pass and stopping it before the ball carrier crosses the line of scrimmage. Vander Esch did an excellent job of using his length to keep himself clean, as he was able to keep the Eagles' right tackle from latching onto his frame and slowing his momentum.

While many will marvel (RIP, Stan Lee) over his speed to the sideline on this play, Vander Esch's ability to quickly key and diagnose the concept is the real secret sauce to his success:

Notice that before Carson Wentz has even given the ball Nelson Agholor, Vander Esch is already starting to move toward the sideline. If Vander Esch diagnoses the play a tenth of a second later, he is likely late getting to the sideline, leaving Xavier Woods in a one-on-one situation with Agholor, which would have likely ended with a touchdown.

The ability to make plays from sideline to sideline is as much mental as it is physical, as linebackers must have the football intelligence to immediately identify the offensive concept and athleticism to put themselves in position to make the play.

Vander Esch has both, and that's one of the main reasons he's been so successful.

Mastery of the basics

There's nothing "fun" about practicing the fundamentals of linebacker play, which is why so many players struggle with the basics early on in their careers. Just like in most athletic endeavors, the fundamentals are the foundation of a player's skill set.

If the foundation was laid scrupulously, it will enhance that player's physical and conceptual capabilities. If the foundation is laid hastily, it will only diminish the rest of his skill set.

It takes a meticulous mindset and hellacious work ethic to master the basics, it's worth it in the end because it allows the player to play to his maximum capabilities.

Though just 22 years old, Vander Esch has shown he has a firm grasp of fundamentals. Many will stand in awe of Vander Esch's size and athleticism, but his proficiency with the basics of linebacker play is what allows him to be so effective on a snap-to-snap basis. This play is a great example:

This play may look simple, but it actually has a high degree of difficulty, as Dion Lewis is a nightmare to tackle in one-on-one situations -- he's ninth among running backs in forcing missed tackles (23). Despite his best effort to avoid Vander Esch with a jump cut, the rookie linebacker was in perfect position to use his giant tackle radius to bring the Titans ball carrier down without much trouble.

The key to Vander Esch making this difficult play look routine is the fact that he A) stayed square to the line of scrimmage and B) came to balance before making the tackle, allowing him to adjust to the elusive running back's jump cut.

Oftentimes, young linebackers (and even a lot of veterans) will fly downhill to make a tackle with reckless abandon. This leads to them reaching the point of contact out of control, making it easy for ball carriers to break or avoid the tackle attempt. By remaining patient, balanced and staying square to the line of scrimmage, Vander Esch was able to make an inherently difficult task look easy.

Defeating blocks

In an age when defenses are getting smaller and faster, the ability to take on and defeat blocks is becoming scarce in the NFL. Teams are favoring the more athletic linebackers who can excel in coverage, rather than the big, lumbering linebacker who can play downhill and destruct blocks on a regular basis.

Here's your monthly reminder that #DallasCowboys LB Leighton Vander Esch is a unicorn among NFL LBs from a size-athleticism point of view. pic.twitter.com/72zPIOu9dB — John Owning (@JohnOwning) November 13, 2018

Luckily for the Cowboys, Vander Esch is essentially a new-age linebacker stuck in a defensive end's body. Not only is Vander Esch more athletic than most linebackers, he's also bigger than most of them.

When you combine Vander Esch's size and length with his lower-body strength and athleticism, it makes him one of the toughest linebackers to block in the league, regardless of age. Fullbacks don't stand a chance of moving him out of a hole:

Really nice job of #Cowboys LB Leighton Vander Esch attacking the block properly (same foot, same shoulder) then squeezing his way by to trip up Blout pic.twitter.com/T1n8gult0k — John Owning (@JohnOwning) October 3, 2018

On this play, Vander Esch is aligned over and responsible for the play-side B-gap. After the ball is snapped, Vander Esch reads the double team from the right guard and center to identify where the run is supposed to go.

Because Vander Esch quickly reads the keys, he is able to attack downhill and meet the fullback at the line of scrimmage. He exhibits perfect technique at the point of contact by attacking the block with the same foot and shoulder, allowing him to exert force on the fullback while remaining balanced and in position to react to the running back's movements.

After blowing up the block, Vander Esch sneaks around the fullback to make the tackle, using his long arms and giant tackle radius.

Coverage

The last reason why Vander Esch's skill set is the best among rookie linebackers is his coverage ability.

At 6-4 with nearly 34-inch arms, Vander Esch is able to condense throwing windows with his frame alone, as his height and length make it difficult for quarterbacks to have a clear path.

Outside of that, Vander Esch has proven capable of performing well in a variety of coverages. Against the Eagles, Vander Esch recorded the first interception of his career while spot-dropping in zone coverage:

Here, Vander Esch is responsible for the hook/curl zone to the near side of the field. Once the ball is snapped, he retreats back to the first-down markers and starts to read Wentz's eyes, looking for any indication as to where the Eagles quarterback will throw the ball.

Once Wentz turns his eyes toward Zach Ertz to start his throwing delivery, Vander Esch widens toward the sideline, allowing him to undercut the throw for an interception. From there, Vander Esch does his best Daryl "Moose" Johnston impersonation as he rumbles downfield (neck roll and all) to give the Cowboys offense fantastic field position.

On top of his ability to spot-drop, Vander Esch is also capable in man and pattern-match, where defenders play zone principles initially before converting to man coverage on the receiver in his zone.

This play is a great example of Vander Esch's ability to succeed using pattern-match coverage:

Gets initial pulled toward the LOS by the PA, but look at the recovery by #Cowboys LB Leighton Vander Esch to retrace and blanket the cross, taking away Stafford's read.



Don't see many LBs that can move like that, especially at that size. pic.twitter.com/C2X5Czz2TA — John Owning (@JohnOwning) October 3, 2018

On this play, Vander Esch gets sucked up to the line of scrimmage a tad by the run action. However, Vander Esch does an excellent job of getting his eyes toward his zone and matching the deep crosser, effectively taking Matthew Stafford's read away and forcing the check-down.

There are only a handful of linebackers capable of making that kind of play in coverage, and Vander Esch is one of them.

And when Vander Esch does allow a reception, he's one of the best at eliminating YAC opportunities.

For comparison's sake, Vander Esch allows an average of 4.11 YAC per reception this season. Luke Kuechly and Bobby Wagner, widely regarded as the two best linebackers in football, allow averages of 4.38 and 5.52 YAC per reception, respectively.

Final thoughts

Not only has Vander Esch been the best rookie linebacker in football this season, he's also been one of the most effective linebackers in the NFL -- period.

Other rookie linebackers definitely deserve recognition, especially Leonard, who is Vander Esch's biggest competition for best rookie linebacker, but none of them make as many plays in as many different situations as Vander Esch.

The Boise State product is the prototypical linebacker from a size/athleticism point of view. He's truly an anomaly -- with only one year of starting experience in 11-man football before this season, Vander Esch is already playing the position better than guys who have been doing it their entire lives. Vander Esch is the perfect mix of old- and new-school traits, and he should only get better from here.

That's a scary thought.

Twitter: @JohnOwning