It was only a matter of time before the hit Houston Texans rookie safety D.J. Swearinger put on Miami Dolphins tight end Dustin Keller this weekend ignited a heated outcry. Keller's teammate, wide receiver Brian Hartline, was the first to fuel the debate. Hartline recently told WQAM radio in Miami that Swearinger's shot -- one that led to Keller sustaining a season-ending knee injury after the defender crashed into his right leg -- was "crap." What Hartline should've been thinking was that it's only a matter of time before another victim winds up in Keller's shoes.

Defensive players around the NFL called this one a long time ago, roughly around the time the league decided to curtail the violence in the game. The belief then, and likely now, was that the more the league's officials tried to limit concussions by penalizing defenders for tackling high, the more those same defenders would start launching their bodies toward the legs of ball carriers. The logic made sense. Offensive players had to go down one way or another. The only question was which body part was going to be at risk.

Houston rookie D.J. Swearinger's tackle left Miami tight end Dustin Keller with three torn knee ligaments and a dislocated kneecap. Kevin Jairaj/USA TODAY Sports

As much as Hartline resented Swearinger's tactics, the bottom line is that the defender made a legal play. It may have broken some unwritten code, but that's not going to gain a ton of sympathy in other circles. Two years ago, Kansas City Chiefs safety Eric Berry sustained an ACL tear after Buffalo Bills wide receiver Steve Johnson plowed into his left knee while delivering a cut block. Offensive players such as Hartline weren't complaining about the devastation Berry suffered at that time.

The reality is that this is the NFL as we now know it and the league would be wise to be just as concerned about what could become a growing trend. If players can't go high, they're going to go low if the circumstances call for it. In the case of Swearinger, he likely was thinking about the best method for tackling an opponent who outweighed him by 40 pounds. It says plenty about Swearinger's character that he sent a sympathetic tweet to Keller after hearing about the consequences of that hit.

What Swearinger also knew was that he now lives in a world in which he can't be nearly as aggressive as he once was. He said he was penalized three times while playing at South Carolina for hits that were deemed too vicious to the heads of opponents. Those types of punishments tend to stick in a player's mind once he's trying to make a living at the next level. Swearinger knew he was crossing the line too much in college and he openly admitted that his hit on Keller had everything to do with avoiding a fine at this level.

The problem with all this rewiring of how players play the game is that there is no perfect method for doing it. The NFL can show videos, fine players, force coaches to teach the appropriate strike zone for hitting and promote their programs for safe tackling all they want. The game is played too fast for all those methods to settle into a player's mindset completely. At some point, defenders are going to do whatever they have to do.

That means the legs are in play. We don't talk about it enough -- and neither do the league's decision-makers -- because it isn't nearly the hot-button issue as concussions are. Most people likely believe that it isn't a big deal if a player loses a season to a knee injury if it means protecting his brain from future long-term trauma. It's a valid argument, and one the NFL seems willing to embrace.