The hit that injured New York Giants receiver Odell Beckham Jr. on Monday Night Football drew gasps around the NFL world. Here was one of the best players in the NFL upended by a low hit in a preseason game with the kind of contact that can cause catastrophic injuries.

Reasonable people can argue whether the hit from Browns cornerback Briean Boddy-Calhoun was necessary, unavoidable, clean or dirty.

But there is no arguing this point: It was 100 percent legal.

Boddy-Calhoun smashed his right shoulder into Beckham's left leg, causing what the Giants said was a sprained ankle. Put simply, there is no NFL rule that prevents a defender from hitting a receiver's leg -- above or below the knee -- in an attempt to tackle him. There are restrictions on where offensive players can block defenders, including clipping and chop blocks, but those don't apply to defenders in the same way.

In this instance, Beckham qualified for protection under the NFL's defenseless player rule because he was attempting to make a catch but had not yet had a chance to become a runner. That protection, however, prevents a defender only from hitting the receiver in the head or neck area or with the crown of his helmet. A defenseless player can still be hit low.

This puts NFL players in a difficult position, of course. The NFL has prioritized rules that minimize or prevent head injuries, so defenders have changed their techniques notably over the years to target their hits below the neck and to use their shoulders and arms rather than their helmets to initiate contact. That lowers the strike zone and can lead to leg injuries in the trade-off.

NFL injury data has shown no dramatic uptick in knee injuries as a result of these rules, but the mantra for defenders is clear: If in doubt, go low(er). Beckham is fortunate that approach didn't lead to a more significant injury.