When the Eagles drafted Harbor in the fourth round in 2010, analysts predicted that Philadelphia scooped up a pair of hands more adept at snagging balls out of the air than pushing defensive linemen out of the way. Two years later, that has proven to be true.
Harbor played wide receiver until his sophomore year of college. And even during those next three seasons, he wasn't exactly facing NFL-caliber front sevens. He played for Missouri State of the Football Championship Subdivision.
"You're faster, stronger, bigger than some of the guys you're going against," said Harbor, who is listed at 6-foot-3, 252 pounds. "Obviously here, that's not going to happen. You can't just go as hard as you can and hit somebody and drive him back. You've got to use proper technique just to give yourself a chance."
In blocking school, Harbor said, leverage is the word of the day. In college, Harbor's coaches told him to focus on one man and outmuscle him. But now he thinks more about where the ball is supposed to go and how to block based on the defense's reaction.
For example, if the play is going to the opposite side and the defensive end, whom Harbor is supposed to block, runs far into the backfield - and far away from the ball - Harbor shouldn't chase after the lineman. Harbor should run up field and try to pick up the safety, who might be the last line of defense between the ballcarrier and the goal line.
Or if running back LeSean McCoy is supposed to take the ball to Harbor's side, he should try to block the end inside. But that's often difficult. If the end is lined up outside Harbor, he should change course and drive the end as far as he can toward the sideline. Then McCoy will cut up field.
In the past, the tight end didn't know that.
On pass plays, Harbor is learning to read the defense better. Depending on how the other team drops into coverage, Harbor should run his route differently.
If, say, the Redskins put both safeties deep, Harbor wants to run toward the middle of the field. That will be a soft spot, and linebackers will do whatever they can to keep him away. Sometimes, they even overcompensate, creating yet another hole in the defense.
Or, pretend the Giants put only one safety deep. The linebackers will want to keep Harbor close to the sidelines. So, the tight end said, he should fight for position inside.
"We never really looked into that at school," Harbor said. "We just went through our basic plays and never really went into the details of the coverages and the things the defenses were giving you."
But no worries, he said. That's the point of postgraduate classes.