Buddy Ryan, the brash and plain-spoken architect of the '85 Chicago Bears defense and a longtime NFL head coach, died Tuesday, his agent told ESPN. He was 82.

The cause of death was not immediately clear. Ryan was diagnosed with cancer in 2011 and suffered a stroke in 2015.

Ryan, the father of Buffalo Bills head coach Rex Ryan and defensive coordinator Rob Ryan, was 55-55-1 in seven seasons as a head coach for the Philadelphia Eagles and Arizona Cardinals.

Ryan made the postseason three times as a head coach -- all while with the Eagles -- but went 0-3.

Ryan, however, was perhaps best remembered as the defensive coordinator for the 1985 Bears team that won Super Bowl XX. Legendary head coach Mike Ditka, speaking on ESPN radio Tuesday morning, credited Ryan’s defensive scheme as the key component that helped Chicago beat New England, 46-10.

“The ’85 Bears wouldn’t have been the ’85 Bears without Buddy Ryan,” Ditka said. “The players absolutely loved him.”

One of Ryan's playbooks called opposing quarterbacks "over-rated" and "pompous" and said they "must be punished."

"A quarterback has never completed a pass when he was flat on his back," Ryan's note said.

Ryan also served as a defensive line coach for the Bills, New York Jets and Minnesota Vikings.

During a single season as defensive coordinator for the Houston Oilers in January 1994, Ryan punched offensive coordinator Kevin Gilbride during a nationally televised game. Ryan was reportedly upset with Gilbride's play calling.

James David Ryan was a Korean War veteran who went to Oklahoma State, then got a master's degree from Middle Tennessee State even while coaching. He got his first major job in the pros in New York, then of the AFL, in 1968. Ryan was the linebackers coach for the Joe-Namath led Jets, a boastful, confident team that fit his personality.

Those Jets led the AFL in defense in his first season on staff, then shocked the Colts in the Super Bowl, 16-7.

"That's something my dad was very proud of," Rex said. "When (former Jets coach Weeb) Ewbank hired him, he had to make a difference. If he felt he wasn't making a difference, then his career as a professional coach would be short."

Instead, it was very long.

Ryan's first job as a defensive coordinator came in 1976 with the Vikings under Bud Grant, like Ewbank a Hall of Fame coach. He spent two years there before moving to the rival Bears, where he concocted the 46 defense that overwhelmed the league with its aggressiveness and unpredictability.

Ryan's defenders, featuring such Hall of Famers as linebacker Mike Singletary and ends Dan Hampton and Richard Dent, came from all angles and was nearly impossible to budge on the ground. Not that teams had more success in the air, either.

"Some say the 46 is just an eight-man front," said Ryan, who named the scheme after safety Doug Plank, who wore that number. "That's like saying Marilyn Monroe is just a girl."

Ditka often feuded during that 15-1 season and Super Bowl run. They nearly slugged it out at halftime of Chicago's only defeat, at Miami on a Monday night in December.

Ryan's work in Chicago got him the Eagles job.

At a meeting the night before the Bears beat New England in the 1986 Super Bowl, Dent said a teary Ryan informed his players that he was going to Philadelphia:

"You guys are going to be my champions. Let's kick some tail," Ryan said.

Hampton then kicked a film projector out of defensive line coach Dale Haupt's hands, and defensive tackle Steve McMichael flung a chair across the room, its legs impaling a chalkboard.

After the 1990 season, Philadelphia routed the Cowboys 27-0 on Thanksgiving Day with hardly any holiday feelings in the air. Cowboys kicker Luis Zendejas claimed Ryan put a $200 bounty on him, something Ryan laughed off as ridiculous.

Arizona hired Ryan  as head coach in 1994 and the Cardinals went 12-20 in his two years there. He never coached again, letting Rex and Rob carry on the family legacy.

The Associated Press contributed to this report.