The evolution of Mike McCarthy's offensive system in Green Bay has led to an expanded running game that isn't just a zone scheme anymore.

Coaches and players alike seem excited about the gap scheme plays that have crept into the Packers' ready list of runs.

Opponents appear to be having some difficulty zeroing in on the more diverse scheme and perhaps as a result the Packers have run the ball better in the first quarter of the season than they have in a decade.

"Our base will always be the zone scheme but we've been working on variations since spring" said offensive coordinator Tom Clements. "We had some successful plays last week man blocking rather than zone blocking. It does have its place."

When McCarthy arrived in 2006 he installed the zone scheme that he had learned from Alex Gibbs in Kansas City and offensive coordinator Jeff Jagodzinski who had learned from Gibbs in Atlanta.

Three or four years into his tenure McCarthy began to add what he has referred to as gap or pattern runs. You'd see a guard pulling every now and again but the sample size was so minimal it was impossible to evaluate.

As McCarthy moved Aaron Rodgers more and more into shotgun formation the traditional two-back sets were used less often. From the shotgun the Packers expanded their package of draw plays too.

In the off-season McCarthy instructed his staff to prepare more gap scheme plays. The high-water mark came Sunday against Detroit when the guards pulled four times and center Evan Dietrich-Smith twice including one on the 67-yard run by Randall Cobb that broke the game open.

"What was great was we were hitting them with different schemes" tackle Don Barclay said. "Gap schemes zone schemes quick hitters. Did a variation of stuff. Outside zone inside zone. We ran the power five to eight times."

In the zone scheme linemen don't pull. Instead they block an area trying to create a wave that leaves ripples for the ball carrier to exploit.

On an inside zone the center and guard usually double-team the one-technique defensive tackle before one leaves to block a linebacker. On an outside zone there is at least one combination block on the play side and cut-blocking on the back side.

In the gap scheme it's more man-on-man blocking with at least one or two angle blocks. There's some form of double team on the front side and a backside puller usually a guard to lead through the hole.

The Lions played a penetrating style of defense with the linemen shooting hard into an assigned gap. Over the years the Packers have had their share of outside zone runs blown up when their linemen weren't able to execute difficult "reach" blocks against defenders aligned in favorable locations.

Now mixing zone with gap runs the Packers have been less predictable. Rather than just fighting off cut blocks on the back side or "reach" blocks on the front side the Lions found out they could get ear-holed by a down block which in effect cuts the defense in half.

"It's a good change-up especially when you're playing against a defensive front that looks to penetrate as much as these guys do" T.J. Lang said Sunday after the Packers rushed for 180 yards. "It's tough to reach block a guy that's firing straight at your head.

"If you can change it up get a double-team on him or get a down block and go around it makes them think about it. It does take them out of trying to penetrate because they have to try to read a down block or power scheme.

"When we do it well it works."

Teams that feature the gap scheme generally have massive tackles and at least one base-blocking tight end because blockers need to generate movement against defensive linemen.

In David Bakhtiari and Barclay the Packers might have the smallest tackle tandem in the league. Matthew Mulligan was that type of tight end but was released Aug. 31.

The athleticism of the Packers' tackles and tight ends make them more suited for the zone scheme's backside cutting and combo blocking.

Lang and Josh Sitton the other veteran guard fit either scheme because of their athletic ability and power. Dietrich-Smith probably is the fastest of the starters but also has the strength to muscle up for gap runs.