The Eagles' base defense for their front seven is a two-gap 3-4. The three down linemen are typically responsible for the running holes on each side of the offensive lineman who is blocking them, hence the "two-gap."
Hart, a defensive end, played at Oregon. It was essentially the same scheme that Kelly and defensive line coach Jerry Azzinaro brought to the Eagles from Eugene. They know Hart well, and he knows what is expected of him.
Allen, a defensive tackle, played in a 4-3 front in his first three years at Wisconsin, but switched to 3-4 nose guard as a senior. Azzinaro recruited him out of high school, and the Eagles brought Allen to the NovaCare Complex for a predraft visit.
A year ago, the Eagles drafted three defensive linemen, and not one played exclusively in college the way the team envisioned using them in the NFL.
They were tweeners. Bennie Logan, selected in the third round, made the transition. Seventh-rounders David King and Joe Kruger did not. King was cut, and Kruger spent his rookie season on injured reserve, although it was more of a redshirt year spent packing on 20 pounds.
Logan played mostly one-gap football at Louisiana State, but the Eagles saw a skill set for playing over center. He's not as big (6-foot-2, 315 pounds) as traditional nose tackles, but he makes up for it some with long arms.
Allen looks the part. He's 6-2, 333 pounds. With Logan slowed by a hamstring injury, Allen has gotten opportunities to go against the first-team offense in camp. He has handled himself well in one-on-one drills against center Jason Kelce.
"Beau, in particular, has got great size for the position of nose, and quick feet to match that size," Eagles defensive coordinator Bill Davis said. "That's really the combination in the NFL. The bigger the body, they can still move their feet, you really get excited about guys."
Logan's job is unlikely in jeopardy. He improved as last season progressed, despite criticism for the Saints' success on the ground in the playoffs. The Eagles didn't fault him, knowing that their scheme did the line no favors.
Allen, though, could eventually chip in against the run - and even the pass, despite his size.
"I think I've been pass rushing pretty well, actually, which is kind of funny," Allen said, "because when you look at me - 330 pounds - you don't think I'm a good pass rusher."
Hart isn't likely to threaten starting defensive ends Fletcher Cox or Cedric Thornton. But he will make it difficult for Kruger to make the 53-man roster.
"Taylor is as consistent as the day is long," Davis said. "Every technique you ask him to do, he does it."
After Hart was chosen in the fifth round and before he had even stepped on an NFL practice field, Kelly guaranteed that he would be a "step above" some Eagles ends in terms of understanding technique.
Hart has prototypical height (6-6) and weight (281) for a 3-4 end, but his arms are shorter than the Eagles prefer. He isn't muscle-bound like some of the other ends, but he's strong enough for the position.
"There's a technique," Hart said. "You don't always have to be the strongest guy out there."
The early confidence the Eagles have shown in Hart and Allen seems to have buoyed them.
"There's always that time when things start clicking, you start knowing the defense, you're not making mistakes, you feel like you're doing the right thing," Hart said. "It's just different for everybody."
They had a head start.