– The Patriots have been accused of spying on opponents and deflating footballs but no one has investigated the tactic most crucial to their success:

Cloning.

Bill Belichick and Tom Brady are the Patriots’ constants. Everyone around them puts the “fun” in “fungible.”

The Patriots’ roster-building formula follows patterns moreso than it pursues elite or expensive talent. In the salary cap era, discovering useful players who fit a system but don’t cost high draft picks or dozens of millions of dollars has allowed New England to become the NFL’s most durable dynasty.

Most dominant NFL teams flame out quickly. The Dolphins won two Super Bowls in a row with Don Shula and Bob Griese. The Steelers of Chuck Noll and Terry Bradshaw won four in six years.

Before the Patriots, the franchise with the greatest dynastic run in the Super Bowl era was the 49ers, who won four titles over 14 years, but they did it with two different coaches and two different quarterbacks.

Brady and Belichick are trying to win a fifth Super Bowl in 16 years. Nobody has ever won that many or contended for titles for so long, and it is bottom feeding that has allowed the Patriots to stay on top.

They haven’t needed the first pick in the draft and have survived losing draft picks to sanctions. Their position prototypes allow them to find underappreciated and inexpensive talent.

“Bill was very, very detailed about the type of players he was going to play with,” said Falcons General Manager Thomas Dimitroff, who worked with Belichick in Cleveland and New England. “He doesn’t try to force-feed a talent into an area on the field that doesn’t suit that player. That’s a massive thing in acquisition.”

Patriots wide receivers tend to be overachievers who are small and not particularly. New England spent a second-round pick on Deion Branch, who was 5-9, and traded second- and seventh-round picks for Wes Welker, who was 5-9, but otherwise have searched for bargains at the position.

Troy Brown, 5-10, was an eighth-round pick. Julian Edelman, 5-10, was a quarterback at Kent State taken in the seventh round. Danny Amendola, 5-11, was signed as a free agent. Chris Hogan, who had 180 receiving yards in the AFC Championship Game, played one season of college football at Monmouth, specialized in lacrosse, went undrafted and is with his fifth NFL team.

The Patriots have employed one superstar wideout in the Brady-Belichick era: Randy Moss. And they got him for a fourth-round draft pick.

Edelman is the prototypical Patriots receiver: a smallish student of the game who can run after the catch, is willing to take punishment over the middle and blocks with abandon.

“The biggest thing for us is our system is broad enough that we try to adapt it and apply it to the guys that we have,” Patriots offensive coordinator Josh McDaniels said. “Whatever their skill sets are and whatever their talents may be, we try to do things that showcase those things or allow them to be successful.”

The Patriots seek similar values at running back. They picked up Corey Dillon when he was 30, Antowain Smith when he was 29 and LeGarrette Blount for the second time when he was 29. The last time they spent a first-round pick on an offensive skill position player was in 2006, when they chose the Gophers’ Laurence Maroney. Maroney disappointed, and Belichick stopped spending capital on backs.

This year’s key runners, Blount and third-down back Dion Lewis, cost the Patriots zero draft picks. Both were street free agents.

Tight end is where Belichick will spend his capital in pursuit of the ultimate offensive chess piece. He got Rob Gronkowski in the second round and Aaron Hernandez in the fourth. He traded a fourth-round pick for Martellus Bennett and a sixth-round pick. He has spent two first-round picks on tight ends: David Graham and Ben Watson.

“They have tried to support me with a strong offensive line, which we have; a solid running game, which we have; receivers who are very versatile, smart and disciplined and we have those,” Brady said. “Tight ends that can do both things in the running and passing games, which we have.

“I think our system tries every week to find different ways to attack the opponent.”

On defense, Belichick is known for unexpectedly dumping seemingly valuable players. Since the end of last season he has traded star defensive end Chandler Jones and linebacker Jamie Collins. Without them, the Patriots finished first in the NFL in total defense.

He got rid of seemingly indispensable players like Richard Seymour and Vince Wilfork when they were playing well but keeps winning. His philosophy: Trade players before they lose value or command massive contracts.

Belichick treats linebackers like tight ends, as defensive chess pieces. He spent first-round picks on his two best linebackers, Dont’a Hightower and Rob Ninkovich, but the player who saved his last Super Bowl victory, cornerback Malcolm Butler, was an undrafted free agent who impressed him in a post-draft tryout camp.

That happens a lot with New England: According to ESPN, they have nearly 54,000 snaps taken by undrafted players over the past decade, the most in the NFL.

“We have acquired a lot of players by trade that we’ve fit into our roster the last few seasons,” Belichick said. “Team building can come from a lot of different ways — waiver wire, draft choices, trades, free-agent signings, street free agents and so forth. Each situation is a little bit different.”

Yet the Patriots’ results are so often the same.