The Eagles lost what their owner described as "a true gem" yesterday afternoon when defensive coordinator Jim Johnson died at the Hospital of the University of Pennsylvania after a bout with cancer that was first disclosed six months ago.

Mr. Johnson was 68.

"There has been no finer coach or man than Jim Johnson," owner Jeffrey Lurie said. "It doesn't get much sadder."

Eagles coach Andy Reid and team president Joe Banner expressed their sadness during a news conference under a tent at Lehigh University in Bethlehem, Pa., where Mr. Johnson had often entertained questions about the team's ultra-aggressive defense.

"At this time, I do think it's important that we do think of the good times that Jim brought us as we go through the grieving process here," Reid said. "Please remember all the positives that he brought to the Eagles and the city of Philadelphia."

Mr. Johnson coached the Eagles' defense through January's NFC championship loss to the Arizona Cardinals. He was replaced Saturday by his longtime assistant, Sean McDermott.

"There is a tremendous sadness," Banner said. "It has been an amazing run with Jim. He has been a great friend and partner, and it has been a tremendous testimony to the life he led from the outpouring of feelings from people. I think his legacy has been the words from the people who knew him best and his family. The Steve Spagnuolos, John Harbaughs and Brian Dawkins and Troy Vincents and the guys who lived with him every day."

Spagnuolo and Harbaugh were assistant coaches to Johnson who went on to head coaching positions in the NFL. Dawkins and Vincent were defensive backs who made his theories work on the field.

When somebody writes an updated history of the Eagles a century from now, Vincent said recently, he knows how the start of the 21st century for the team should be chronicled.

"In that chapter of Eagles history, there can be no argument that you look at the defensive coordinator and you look at No. 5," Vincent said. "Jim Johnson and Donovan McNabb are the staples to Andy Reid's success."

During his 10 seasons as the Eagles' defensive coordinator, the team played in five NFC championship games and one Super Bowl, and won five NFC East division titles. Mr. Johnson's zone blitz packages became one of the team's trademarks of success.

"Think about what you'd hear from Troy Aikman every time you'd turn on an Eagles game," Vincent said before going into an impersonation of the former Dallas Cowboys quarterback and current Fox color analyst. " 'You better believe this defensive coordinator is going to bring the heat. This quarterback will see pressure. This young quarterback will be tested and if he shows any signs of weakness, he will be in trouble against this Jim Johnson defense.' "

The Eagles were an awful team with a no-pressure defense when Reid became the head coach and hired Mr. Johnson as his defensive coordinator in 1999. They remained an awful team that season, winning just five games, but the defense sprung to life.

After forcing a league-low 17 turnovers in 1998, Ray Rhodes' final season as head coach, the Eagles led the league with 48 takeaways, including 28 interceptions, during Mr. Johnson's first season as defensive coordinator.

By 2001, when the Eagles went to their first of four straight NFC championship games, the defense was ranked among the best in the NFL in almost every category.

With few exceptions, the Eagles' defense remained an elite unit, including last season, when the team had the NFC's top-ranked defense.

"As a defense, we knew we could play," former Eagles linebacker Ike Reese said. "What we needed was direction and structure."

The Eagles' defense had 26 Pro Bowl selections during Mr. Johnson's tenure, including seven by safety Brian Dawkins.

"He changed the way safeties played in this league by the way he used Brian Dawkins," Reese said. "When you look at Troy Polamalu and Ed Reed and how people use guys at the safety position, that's because of the way Jim Johnson used Brian Dawkins."

All five of Vincent's Pro Bowls came during his years with Mr. Johnson as the defensive coordinator.

"I still remember that first meeting, and talking to him about his philosophies," Vincent said. "Jim's enthusiasm and attack style was a culture change. He just brought a sense of 'This is who we are.' It was the first time I had been introduced to a zone-pressure defensive philosophy. He allowed me to flourish. His scheme and his belief in me allowed me to take my game to the next level."

Hugh Douglas also emerged as a star under Mr. Johnson, although the Eagles' two-time Pro Bowl defensive end used to test his coach's sanity.

"Hugh used to drive him crazy," Vincent said.

Douglas pleaded guilty to that charge.

"I'll never forget, we were putting in a defense and I messed it up," Douglas said. "I messed it up every practice. He kept cursing me: 'Damn it, Douglas, we're going to run this defense until Hugh Douglas gets it right.' So we'd run it again, and I'd still [mess] it up.

"Jim says, 'All right, we're going to put this wing stunt in right here because it works better for the defensive end.' Everybody knew what he was doing. They were all saying, 'Yeah, Hugh keeps [messing] up the defense and that's why Jim put it in.' I was the founder of the wing stunt because I kept messing up the defense. He knew I did some things unorthodox, so he made up things for me to be free when I played."

Leslie Frazier, Ron Rivera and Spagnuolo were three defensive assistants who went on to become a defensive coordinators elsewhere after working under Mr. Johnson. Spagnuolo is now the head coach of the St. Louis Rams, and Harbaugh, who also worked under Mr. Johnson, is the head coach of the Baltimore Ravens.

Born in 1941 in Maywood, Ill., Mr. Johnson played quarterback for coach Dan Devine at the University of Missouri.

"I remember recruiting him," Devine told The Inquirer in a 1999 interview. "We were really after his neighbor, who was one of the top players in the country. When they visited, we paid all the attention to the other kid and kind of neglected Jim. As it turned out, Jim was one of our best players. After being a defensive halfback his junior year, he was our starting quarterback his senior year."

After a two-year stint as a tight end with the Buffalo Bills in the American Football League, Mr. Johnson turned to coaching in 1967, when he was hired as the head coach by Missouri Southern College. His two-year stint there would be his last as a head coach. From that point on, it was his defensive mind that attracted suitors.

He moved to Drake University and then to Indiana University, then reunited with Devine in 1977 when he took the job as defensive coordinator at the University of Notre Dame. The Fighting Irish, with Joe Montana at quarterback, won the national championship that year. When Devine stepped down a few years later, he said he suggested Mr. Johnson as his replacement, but Gerry Faust got the job instead.

Mr. Johnson first coached professionally in the U.S. Football League before landing a job with the St. Louis Cardinals as a defensive line and defensive backs coach in 1986. He moved from there to the Indianapolis Colts in 1994, which is where he caught the eye of a young quarterbacks coach from the Green Bay Packers during a 1997 game.

"We sacked the quarterback quite a bit in that game and we got some touchdowns off blitzes," Mr. Johnson said during an interview. "When Andy got the head job here, he called me. I didn't know him that well. But Andy called me for an interview."

That interview led to one of the finest decades of defensive football in the Eagles' history, and when the chapter about the top of the 21st century is written about this football team, the name of Jim Johnson will be mentioned prominently.

Mr. Johnson is survived by his wife, Vicky; a son, Scott; and a daughter, Michelle, and four grandchildren.

Plans for funeral services were pending.