We've noted on several occasions the stunning success of the Green Bay Packers' play-action game, which continues to hum along at high efficiency even though the Packers don't run very often or for huge chunks of yards.

John McTigue of ESPN Stats & Information has forwarded some revealing microanalysis that helps explain the Packers' success. In brief: Much of the Packers' play-action success has come from a moderately-used formation that ordinarily tells defenses the Packers are going to run.

The Packers are mostly known for using three receivers, one tight end and a running back. But since the start of the 2010 season, they have employed a backfield set of at least two running backs on about 38 percent of their plays.

Normally, that set suggests a running play. In fact, according to McTigue, the Packers have run on about two-thirds of those occasions. Conversely, they've passed on about 73 percent of plays when they've had one or less running backs on the field. In other words, the Packers run on two out of every three plays with multiple running backs on the field and pass on seven of 10 plays in all other formations.

So the explanation is pretty simple when you think about it. As the chart shows, the Packers are hitting most of their big play-action passing plays when in multiple-back formations. In Sunday's 30-23 victory over the Carolina Panthers, both play-action touchdowns came with two running backs in the backfield. If you're a defender trying to get a jump on the play, it would make sense to expect run in those instances based on the tendencies we just described.

Naturally, NFL teams look for trends among their opponents. But they know their own tendencies better than anyone. In this case, the Packers exploit that knowledge to their own benefit.

That happens routinely in the NFL, and I don't want to imply the Packers are the only team to figure it out. But it's not often that we can illustrate it so plainly. Credit goes to McTigue for spotting this one and ferreting it out.