So the first challenge for Davis, head coach Chip Kelly, and the personnel staff is tricky: weed out the softies and figure out which players have the innate qualities it takes to play on a championship defense.
"I think you have to pick them that way," Davis said. "I think you have to do your research and pick players that have a tough mentality and tackle well."
That process may have begun last year, with the drafting of defensive lineman Fletcher Cox and linebacker Mychal Kendricks and the trade for linebacker DeMeco Ryans. Those three are among a minority of players who fit Davis' bill.
The coaching staff can't perform personality transplants, but it can establish a culture where contact avoidance and halfhearted effort are not accepted.
"I never assume a player has any fundamental background at all," Davis said. "From the ground up, we're teaching fundamentals, from tackling to eyes to alignment to everything. I assume that you know nothing. I don't care how many Pro Bowls you've been to. You're going to get coached. You're going to get taught. You're going to get the work that makes you better.
"Every vet, every Pro Bowler I've coached, they love it. You coach them all, and they eat it up. The worst thing you can do is not coach a great player."
One theory: In establishing the very good Eagles defenses of the early 2000s, Jim Johnson and his staff took that approach. As driven players like Brian Dawkins, Jeremiah Trotter, and Troy Vincent became entrenched, they held younger players to a standard. The coaches didn't have to be as hands-on. As those players aged out, and with Johnson's death in 2009, the continuity was broken.
By 2012, you had Todd Bowles lamenting that his team couldn't execute basic high school coverage schemes.
The worst offenders, big-money cornerbacks Nnamdi Asomugha and Dominique Rodgers-Cromartie, should be the first players out the door. The fact that Rodgers-Cromartie went to a Pro Bowl when Davis was his defensive coordinator in Arizona does not erase his crimes against football over the last two years.
Frankly, Davis didn't sound all that excited about the enigmatic Rodgers-Cromartie - and he sounded fired up about almost everything.
"I know DRC," Davis said. "We drafted him. As a young guy, he went to the Pro Bowl. He made a lot of plays. We had some success in Arizona with some pressure packages and got a lot of turnovers, and we created some defensive scores, and Dominique was part of that."
Davis may simply be cautious about publicly endorsing players before he knows what Roseman and Kelly have in mind. But Rodgers-Cromartie has been exactly the kind of player this team should not build around.
It is going to take time for Davis to figure out what he has to work with and what defensive scheme fits best. It is going to take more talent. The reality is, he is not likely to build the kind of smothering defense the Eagles had when his father was working with Gamble's father.
The NFL has changed too much. That tough, physical defense in San Francisco gave up 29.7 points per game in the postseason. It is an offense-oriented league. A defense has to minimize big plays, create some turnovers, and buckle down in the red zone. It just has to give its own offense a chance to pile up more points.
That's the job Davis was brought here to tackle. He has to be better at it than the players he inherited.
Contact Phil Sheridan at email@example.com, or follow on Twitter @Sheridanscribe.