While the Eagles relied heavily on play-action last year, their level of effectiveness varied, depending on what Michael Vick did with the football.

Football Outsiders released some interesting data recently, showing that the Eagles used play-action on 25 percent of their pass plays, third-most in the NFL, behind only Houston (33 percent) and Minnesota (29 percent).

Here is a look at the Eagles' yards per play when they used play-action.

As a point of reference, the Eagles averaged 6.2 yards per play (fifth) and 7.7 yards per pass attempt (11th).

The data also includes a breakdown of how each team performed on actual passes off play-action. In other words, take away sacks and quarterback runs. The Eagles averaged 8.2 yards per pass attempt on play-action.

Football Outsiders' main statistic is DVOA, which, in its simplest sense, measures performance against the league average, attempting to account for a number of variables. The Eagles' DVOA when using play-action was 9.3 percent. But their DVOA on play-action passes was -0.2 percent. That suggests a lot of the success the Eagles had when running play-action came when Vick took off and ran with the ball.

Overall, Vick took off and ran 53 times on designed pass plays and averaged 10.2 yards per carry, a huge number. But he was also sacked 23 times for a loss of 126 yards. If you add up both numbers - meaning every play where Vick dropped back, but didn't attempted a pass - the average was 5.4 yards.

One more set of numbers: Football Outsiders listed DVOA on pass plays that did not include play-action. The Eagles and Vick fared very well at 28.0 percent. Only the Chargers, (29.4 percent), Steelers (30.3 percent), Giants (41.3 percent), Patriots (53.2 percent), Saints (55.8 percent) and Packers (71.3 percent) had higher DVOA numbers on non play-action passes.

The Eagles actually ran play-action more (25 percent of the time) than they did in 2010 (20 percent). On one hand, those plays often give Vick space (either outside the pocket or deep behind the line of scrimmage) where his passes are less likely to be batted by opposing linemen. They also (ideally) allow the receivers to get downfield. Matt Bowen of the National Football Post recently broke down one of the Eagles' play-action pass plays in which DeSean Jackson runs the deep post and Vick rolls out to his left.

The play-action caters to Vick's improvisational style and allows him flexibility if he sees a running lane.

On the other hand, if the opponent is not fooled, Vick sometimes has pressure in his face as soon as he turns around. On non play-action throws, Vick never has to turn his back and can survey where defenders are moving from their pre-snap positions.

One more thing to keep in mind: Vick often rolls to his left on play-action passes. That side used to be anchored by Jason Peters, but it will now be Demetress Bell at left tackle in 2012. At training camp, I'll try to get a sense of how that change could affect the offense's plans in terms of using play-action.

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