PHILADELPHIA ( - When the Eagles practice you can look across the field and see a card to designate the formation Doug Pederson and Frank Reich want for their offense.

The default reads "11" to signify the team's base offense should be on the field, which includes three receivers and one running back or in NFL parlance "11 personnel," referring to the one RB and one tight end on the field.

Because Pederson is big on formational football, you'll also see plenty of 12 personnel (one back and two tight ends ) and even some 13 personnel and 21 (two backs, a tight end, and two WRs).

When Philadelphia adds the "P" on the end of the latter, it stands for 21 pony, meaning the two backs on the field at the same time should be the diminutive Darren Sproles couple with undersized rookie Donnel Pumphrey.

Usually when you play with two backs, it's a tailback running behind a fullback but the Eagles think they have something in the 175-pound Pumphrey, the NCAA's all-time leading rusher, and obviously understand how explosive Sproles can be.

Because of their size limitations, however, unless you start thinking outside the box when one is in the game, the other can't be.

To that end, Pederson has spent much of the spring experimenting with the idea of getting both on the field at the same time.

"The amount of running backs that we have and trying to get everybody reps, it's a great way to get two running backs on the field at the same time and get guys reps," Pederson told when discussing the formation. "It also allows us to see what Donnel can do away from the formation or in a receiver position."

When it does happen, it's usually Sproles in the backfield and Pumphrey split out wide, usually in the slot.

The tweaks continued during the opening of the team's mandatory minicamp on Tuesday and when 21P came out late in practice, it was Pumphrey outside the numbers and Sproles behind Carson Wentz.

At the snap, Pumphrey retreated into the backfield to feign a reverse as Wentz went play action with Sproles, giving Jim Schwartz's defense two decoys to worry about.

On this occasion, it didn't work as the pass rush got home on the slow-developing play so there are still plenty of hiccups to work out of Pederson plans to utilize this personnel grouping come September.

"How does that fit into the system?" Pederson asked rhetorically. "Those are all things that we can get on tape here in practice and make those decisions once we get into camp and then on into the regular season when it comes to game planning."

-John McMullen covers the Eagles and the NFL for You can reach him at or on Twitter @JFMcMullen