The 76ers have long possessed the athleticism necessary for defense.

They're young, they're fast, and their roster is filled with swingmen whose contracts were earned because of wide wingspans and soaring verticals.

But what the Sixers haven't possessed - not until this season, anyway - is a blueprint to harness those qualities to produce ball pressure, competent rotations, and intelligent weakside reactions.

The previous few seasons have been filled with low-IQ defense. We've seen games filled with an unguarded three-point line, to the point where the only rational explanation for such pathetic defense was either a lack of effort or a radical omission of defensive drills from the practice schedule.

For much of last season, it was a combination of the two.

Today, we see something different.

We see understanding, we see proper rotations, and we see confidence in the dependability of the next line of defense. Couple that with the team's natural speed and agility and the result is a lineup that should manage to keep itself in almost every game.

How did this happen?

Anyone watching this team since Sept. 28 knows that it's been an evolution of sorts.

Implementing a defense is a little like designing a map. You create the map, you create the directions, you create the key, and you distribute it to the players. You show them why one road (i.e. forcing penetration toward the baseline) will lead to the desired exit (i.e. forcing baseline help and limiting the offense's options).

If the map you distribute is poorly designed, or there are crisscrossing roads and confusion, or you forget to actually spend time explaining how the map works, the players are soon going to realize that following your directions leaves them lost and stranded.

At that point, they'll throw away the map. Almost every member of last season's team did this.

This season, the map was simple: Here's what we do every time the ball goes into the post; this is what we do each time there is a pick-and-roll; every time you're on the weak side we want you here.

And then there were practice drills, without confusion, until the rules of the map became subconscious reactions by all the players.

For the first chunk of this season, there were no opponent-specific alterations. Head coach Doug Collins and associate head coach Michael Curry needed proof of the team's absorption of the aforementioned fundamentals before they started tinkering with scout-specific defensive game plans.

It's only now that the Sixers will adjust their defense for another team's weapons - like going under a pick-and-roll involving a penetrator or sticking tighter on the weak side if guarding a deadeye shooter.

At this point, tailoring the defensive game plan should be like placing a cup on a sturdy table: The foundation is solid so there's no reason this little addition should shake the core.

And after each game, the coaching staff breaks down every defensive possession and every player within that defensive possession.

They then chart the results.

When the players arrive at the Philadelphia College of Osteopathic Medicine for practice, Curry has posted on a white board each player's defensive grade: 87 percent if you were in the correct defensive possession 87 percent of the time, 64 percent if you were in the correct position a little less frequently.

It's the first thing guys do when walking into practice the day after a game. And those numbers likely stick in each player's mind when he steps onto the court.

When taking over at the beginning of the season, Collins and Curry instituted two defensive changes that have been crucial in limiting opponents' field-goal and three-point percentage: double-teaming as the exception, not the rule, and drilling the 2.9.

If a team is continually effective on the low block, as the Los Angeles Lakers showed with Lamar Odom on Friday night, the Sixers will send a double-team in an effort to make the opponent beat them somewhere else. But this happens only when forced, and not before a player has proved worthy of the ensuing defensive scramble. Sixers fans should consider this the primary reason for the improvement in three-point field-goal defense.

Although most folks watching an NBA game follow the ball, the majority of a team's defense is dependent on its weakside positioning: Collins says the ratio of importance is 70 percent weak side, 30 percent ball side.

That's where the 2.9, as in 2.9 seconds, comes into play.

In the NBA, if you're in the lane on the help side - meaning the man you're guarding is on one side of the floor and the ball is on the other - for three seconds, it's a technical foul and the opponent gets a free throw.

But if you're in that position for 2.9 seconds, slipping in and out of the lane but still providing the necessary weakside presence, you've gained a defensive advantage.

Entering this season, it was on the weak side where the Sixers were in disarray. Guys were sticking to their men, they were late on rotations, or they were fully committing to routine double teams. The crucial in-between, which keeps the offense guessing and demands split-second decisions by the ball handler, was absent.

It's easy to say you're going to be all about defense. Every team says that.

But the Sixers are actually doing it.

Inside the Sixers:

Read Kate Fagan's 76ers blog, "Deep Sixer," at http://go.philly.com/dsix.

Blog response of the week

Subject: The emergence of Spencer Hawes

Posted on Dec. 15, 2010, at 8:14 a.m.

By Delaware Mike

Somebody pinch me . . . Phillies get [Cliff] Lee back, unbelievable! So the Sixers ARE becoming a real NBA team and the Phillies, Flyers and Eagles all have legitimate chances to make it to championships . . . this hasn't happened since the early '80s!

GO PHILADELPHIA!!!!

Contact staff writer Kate Fagan at 856-779-3844 or kfagan@phillynews.com.