For those who haven't heard, Texans DT Travis Johnson, who has 1 career sack in 28 games after being drafted 16th overall out of Florida State, knocked Trent Green unconscious Sunday when his knee slammed Green's temple while Green was trying to make a block on an end around. Johnson then stood and flexed over Green's prone body, and then criticized Green for making a low block after the game, saying Green, who says 217 lb. to Johnson's 305, should have tried to block him high.
Obviously, there's no way for Green to block Johnson above the waist. And if he tried, Johnson would have actually tried to concuss him, although he probably would have failed. And the block wasn't dirty - you see low hits and blocks all the time on size mismatches in the NFL. What's somewhat ironic is that Houston head coach Gary Kubiak was the offensive coordinator for the Broncos for 11 seasons, where his offensive linemen ruined the career of many a defensive lineman with illegal chop blocks.
A chop block is when an offensive player dives at the knees of a defensive player from the side or behind while that defensive player is engaged with another offensive player. The benefit is that the defensive player is distracted, looking down and to the sides instead of straight ahead or at the ball carrier. If Travis Johnson is cut by a player straight ahead of him, then he should look where he's going.