ESPN's Greg Schiano, Ryan Clark and Tim Hasselbeck break down what each undefeated NFL team should be worried about as the season progresses. (2:17)

A good way to evaluate the top teams in football is by counting how many draft choices those franchises have signed to second or third contracts.

The Green Bay Packers are the best. They have 14 on the roster. The Cincinnati Bengals are next at 13. The New England Patriots are third at 10. What do the three teams have in common?

They are currently unbeaten. Again: the teams that have been the best about retaining their draft picks into multiple contracts are a combined 17-0 so far.

On the flip side, teams at the bottom of the list are naturally struggling. The Chicago Bears are 2-3, and halfback Matt Forte is the only remaining draft choice signed to a second contract. The Jacksonville Jaguars are 1-5 and have only two on the roster. The past two drafts have improved the Oakland Raiders, but they can count only three -- halfback Taiwan Jones, kicker Sebastian Janikowski and the return of safety Charles Woodson.

The lack of draft choices worthy of extensions forces these teams to constantly hit the dangerous free-agent market for solutions -- which often don't work out.

The formula for success appears to be simple, but it's hard to execute. Draft well. Target the best draft choices and sign them to extensions. Build a homegrown talent pool.

Packers general manager Ted Thompson has been the best at following this system. Thompson continues to stock great players around quarterback Aaron Rodgers with smart drafting and intelligent cap management. Thirty-five players on the Packers' 53-man roster are from the draft. Four draft choices, including starters Jordy Nelson and Sam Barrington, are on injured reserve.

Ted Thompson (right) has used the draft to build a strong foundation in Green Bay. AP Photo/Morry Gash

The stability of Thompson's work has allowed head coach Mike McCarthy to keep the Packers in Super Bowl contention every season. It's allowed him to build and maintain one of the best offensive lines in football. It's prevented the Packers from leaning on free agency, which could lead to mistakes and wasted money that eats up cap room.

It's no wonder the Packers are a heavy NFC favorite.

The Patriots are selective in the draft choices they re-sign, but they have created an environment in which players might take a little less to stay. And why not? The Patriots have ruled the AFC East since Bill Belichick took over as coach and Tom Brady became the quarterback in 2000. Stay with the Patriots and eventually you will win a Super Bowl ring.

Mike Brown's Bengals, 6-0 this season, are the biggest surprise entry into this elite class of retention franchises. They have created a homegrown talent pool that is peaking. They have been to four consecutive playoffs and are competing against New England and Denver for top seeds in the AFC playoffs.

It's taken until this year for people around the league to recognize how deep and talented the Bengals' roster is. The Bengals lead the NFL with 38 drafted players on their 53-man roster. They have four other drafted players on injured lists, including first-round pick Cedric Ogbuehi, who is considered their left tackle of the future.

The Bengals' roster is so deep they had the luxury of taking a tackle who wasn't expected to play this season because of a knee injury.

"I don't think it's a new idea -- draft and retain,'' said Bengals director of player personnel Duke Tobin. "You have to draft well. Beyond that, you've got to develop the guys and put them in the place to succeed. That's what our coaching staff has done.''

The process is no different in Green Bay, New England, Cincinnati, Seattle or Denver. It all starts with the draft.

Star WR A.J. Green is one of many successful Bengals draft picks since 2011. Kirby Lee/USA TODAY Sports

Let's take a closer look at the Bengals. Part of the problem of going to four consecutive playoffs is drafting in the final 12 spots of the first round. By then, top pass-blocking talents, quality pass-rushers, No. 1 wide receivers and quarterbacks are gone.

"It's a challenge when you draft lower,'' Tobin said. "But honestly, it widens the pool of guys you can choose. When you are in the top 10, there is a very small group of players who are acceptable and sometimes they don't match up to what you need. When you are down at the bottom, the field gets bigger. There are a lot of choices.''

Tobin maximized the Bengals' high position in the 2011 draft by taking wide receiver A.J. Green in the first round, quarterback Andy Dalton in the second and guard Clint Boling in the fourth. All three started. All three have received contract extensions.

In 2012, the Bengals added cornerback Dre Kirkpatrick, guard Kevin Zeitler, wide receiver Mohamed Sanu, defensive tackle Brandon Thompson, wide receiver Marvin Jones and safety George Iloka. This group has been so good, it's going to be hard for the Bengals to retain them all. All but Kirkpatrick are up for free agency next season.

"The first thing we do in the pre-draft process is try to build a consensus,'' Tobin said. "If we can't build consensus, we usually move on to a different guy. We don't want guys to come in where half the guys don't think he can do it. We come up with a list of guys we all feel good about.''

That's the draft process. A harder part might be the retaining process. The current CBA forbids contract talks until a rookie's fourth and final year of his contract. Teams can place a fifth-year option to keep a first-rounder, but players taken from Rounds 2 through 7 look to free agency and the big dollars.

"You can't retain everybody,'' Tobin said. "You can't have a team filled with guys being paid at the top level of every position. As long as you draft well, the ones who leave, you can try to replace. But I don't think you can sustain success going out and getting free agents. I've never seen a team do it.''

Initially, the Bengals knew it was going to be hard to keep defensive end Michael Johnson, whom they franchised in 2013. Knowing that, the Bengals signed defensive end Carlos Dunlap to a five-year, $39.3 million contract with the hope they could find a way to keep Johnson.

They couldn't. He ended up signing a five-year, $43.75 million contract with Tampa Bay, but he was cut after one season. Johnson returned to the Bengals for $5 million a year and the Bengals received a third-round compensatory pick for his short-term departure to the Bucs.

Unlike many teams that would ask players with declining playing time to take pay cuts or get cut, Bengals management is letting the players play out their deals. Leon Hall, formerly the team's No. 1 cornerback, signed a four-year, $39 million contract extension in 2011. His role this season has been more of a backup and the team might move him to safety.

The Bengals have let him have that role at $7.7 million this season.

"I know guys like T.J. Housmandzadeh and others who have gone elsewhere for bigger contracts [but] have come back here and said, 'I would have been better to stay here,''' Tobin said. "Here, you earn the contract you get.''

The Patriots have taken back safety Patrick Chung. Once wide receiver James Jones was released by two teams this summer, he had no problem coming back to the Packers at minimum salary. The Bengals were able to get Johnson and defensive tackle Pat Sims back on their rosters after the players went to other teams in free agency.

Draft and retain. Not a bad action plan.