Kelly's stated preference and Davis' history, along with the buzz at the NFL combine this past week, have made it evident that the Eagles will have a very different scheme, one that needs players they don't have.
In the 4-3 "under" defense that Davis ran in Arizona from 2009 to '10, Bertrand Berry and Travis LaBoy - similarly sized at 6-foot-3 and about 250 pounds - started off as his primary predators.
Bradley, who answered questions Saturday at the combine, described his ideal Leo.
"It needs to be somebody who has good speed," the new Jaguars coach said. "A guy like [former Eagles and current Seahawks end] Chris Clemons . . . that type of individual who is maybe 6-3, 250 pounds and can run a 4.5, 4.6 [40-yard dash]. Some teams may consider that a linebacker type."
While the predator is primarily a pass rusher, he can occasionally drop into coverage and move about the line in a two-point stance, hence the 3-4 "look" of the 4-3 "under."
The Eagles don't have a prototypical predator, but general manager Howie Roseman said last week that Trent Cole or Brandon Graham could easily transition into an outside- linebacker position.
They don't have ideal dimensions (Cole is 6-3, 270, and Graham is 6-2, 268), have generally rushed the passer from a four-point stance, and aren't cover guys. But the predator's primary responsibility is to pin his ears back, and both ends could thrive in that role.
Second-year defensive end Vinny Curry (6-3, 266) and recently acquired CFL pass rusher Chris McCoy (6-3, 261) are other possibilities.
If Davis is to employ a similar defense, he's going to need 3-4 outside linebackers. On the strong-side, the outside linebacker rushes about 70 percent of the time and drops into coverage the rest of the time.
There are plenty of candidates in the draft, including Oregon's Dion Jordan. The obvious connection to Kelly has many slotting the 6-6, 248-pound 22-year-old to the Eagles with the fourth overall pick. That may be a little early to take a player who is considered a bit of a project, slight at 248 pounds, and is expected to be sidelined for three to four months after he undergoes surgery Monday on a torn labrum.
Florida State's Bjoern Werner (6-3, 266), Texas A&M's Damontre Moore (6-4, 250), and Louisiana State's Barkevious Mingo (6-4, 241) - also potential 3-4 outside linebackers or predator defensive ends - are projected to go within the first 10 picks.
The Eagles under Andy Reid drafted defensive ends on the shorter side for their 4-3 scheme, players often described as "high-motor" guys who had a low center of gravity. They specialized in pass rushing, and when the Eagles switched to the wide-nine scheme on the defensive line two years ago they were asked to do very little other than get after the quarterback.
But it became predictable. The 3-4 or the hybrid creates confusion for offenses because they often don't know who that fourth rusher is on passing downs. Along with the predator and the outside linebacker, there are also a strong-side defensive end and a weakside defensive tackle (which would be Fletcher Cox) who are at the line in Davis' 4-3 "under."
Either the predator or the outside linebacker could drop while a middle linebacker or weakside linebacker blitzes.
"You see a lot of teams that might be 3-4, but on third down, they show some 4-3 principles," Bradley said.
On run downs, Davis' 4-3 "under" has a nose tackle. Bradley's run scheme has both 4-3 and 3-4 principles, but there is also flexibility to pass-rush out of those formations, which is why the outside linebackers are so important in a hybrid defense.
The Eagles need to get some.
Contact Jeff McLane at email@example.com, or follow on Twitter @Jeff_McLane.