Louis Riddick shares his disgust for Titans WR Harry Douglas' low hit on Broncos CB Chris Harris Jr., saying that in the past defensive backs would be hunting him down for a hit like that. (1:25)

A regular analysis of strategy, decisions and calls that impacted the week of NFL play. (From Sunday: Referee Jeff Triplette appeared to call a penalty on the wrong team during Detroit's 20-17 victory against Chicago.)

There is a difference between "dirty" and "illegal," a distinction that seemed to vanish Sunday amid the reaction to a low block from Tennessee Titans receiver Harry Douglas on Denver Broncos cornerback Chris Harris Jr.

Douglas' block was legal, no matter how you look at it or whom you ask -- and despite the labyrinth of NFL rules designed to minimize dangerous contact. It is a completely different question, and almost entirely subjective, to ask if Douglas acted with malice in an attempt to "end my career," as Harris said after the game.

Let's unpack this hit with the dispassion necessary to separate the issues of what's allowed and what's simply frowned upon.

The fireworks began in Nashville in the second quarter at Nissan Stadium. Douglas, lined up on the left side of the formation, was assigned to block Harris on what turned out to be a six-yard run by Titans tailback Derrick Henry.

At the snap, Douglas jogged eight yards downfield. Harris was moving slowly toward the ball. In a sudden move, Douglas dove toward the bottom of Harris' right leg to block him from getting any closer to Henry, whose run took him almost directly up the middle.

At the moment of contact, Harris and Douglas were perhaps 10 yards away from Henry. Harris immediately fell to the ground, clutching his leg. He left the game but later returned, apparently uninjured.

There are a handful of rules that prohibit low hits in certain situations during NFL games, but quite simply, none of them applied in this situation.

It wasn't clipping, which is blocking an opponent below the waist from behind. Douglas' entire body was in front of Harris when contact was made.

It wasn't a peel-back block, which is penalized when a blocker initiates contact from the side. Again, Douglas approached Harris from the front.

And it wasn't a chop block, a penalty that requires contact from two offensive players -- one who hits high and the other who hits low -- on either a passing or running play.

So if you believe the hit was illegal, and that the NFL should punish Douglas with "whatever the biggest fine is," as Harris said Sunday, then you must identify the rule Douglas broke. There is none.

"From a rules standpoint," former NFL officiating chief Mike Pereira, said Sunday night on Facebook Live, "it is not a foul." Pereira is now an analyst for Fox Sports.

Former NFL officiating supervisor Jim Daopoulos told me via text Sunday night: "Really didn't like it, but it was legal and not a foul."

It's easy to understand why Harris was surprised. Most receivers are not strong blockers, and they don't always give much of an effort on running plays that aren't directly behind them. It's more common to see a receiver simply reach for a defensive back, trying to slow him down, than actively cut block him.

Douglas gave every indication that he would attempt nothing more than a passive block as he jogged off the line of scrimmage. He sprang into action in a way that you don't often see. Harris was jogging slowly toward the pile, but he said he was "nowhere near the play" at the time of contact.

Though it might not have been necessary or common, the cut block is still a legal option in those situations. Douglas told reporters that he makes a habit of it.

"I guess he didn't watch film," Douglas said, "because if they watched me last week or any other game, he would say that's what I do in the run game."

Why use a cut block instead of putting his hands on Harris' chest and driving him away from the pile? There are plenty of reasons to use the low technique. It is the most efficient way to get a defensive player on the ground, and, if nothing else, it forces him to redirect his progression to the ball in order to avoid the contact.

It also minimizes the chances of a penalty, either by holding or perhaps making contact with the head and neck area.

There is only one person on the planet who knows whether Douglas actually tried to injure Harris. His technique was aggressive but legal. Again, Harris probably wasn't making the tackle even if Douglas never tried to block him. It's understandable that he was angry to have, in his mind, narrowly avoided serious injury on a play where he had little chance of making a tackle and with a technique that many receivers wouldn't use in that situation.

NFL players have a common-sense responsibility to look out for one another. The game is dangerous enough without using techniques that unnecessarily elevate the possibility for injury. The Broncos clearly perceived Douglas to have violated that obligation.

That might make his block dirty, but it is legal under NFL rules. And if it's legal, it's something that Harris must expect, prepare for and ultimately accept -- however unlikely or excessive it might be.