There are 21 coaches in the NFL Hall of Fame, all of whom were head coaches at some point in their careers.

There aren’t any who were known for their time as an assistant. But one could make a pretty strong argument that Philadelphia Eagles Defensive Coordinator Jim Johnson should be the first.

Johnson, who took a leave of absence from the team in May to fight a cancerous tumor on his spine, died, the team announced Tuesday. The 68-year-old coach designed an attacking defense that helped lead the Eagles to five NFC Championship games and a Super Bowl. They were generally among the league’s top defenses and he was considered among the top defensive minds in the league’s history.

According to ESPN, his 10-year tenure produced 26 Pro Bowl players and 390 sacks, good for second in the league during that time period. He was a master architect of blitzes and was revolutionary in his ability to keep offenses off balance. He never became a head coach in the NFL, but his proteges, John Harbaugh and Steve Spagnuolo, have head jobs right now.

The accolades for Johnson are pouring in from around the league at NFL.com and other locations.

“For 10 years, Jim Johnson was an exceptional coach for the Philadelphia Eagles, but more importantly he was an outstanding human being,” Eagles Owner Jeffrey Lurie told ESPN.”As an integral part of the Eagles family, Jim epitomized the traits of what a great coach should be – a teacher, a leader and a winner. … It was easy to feel close to him.”

“When people talk about the Andy Reid regime here, that wouldn’t have been possible without Jim,” Coach Reid said, according to CBSSportsline.com. “I think we all understand that. He really represented everything this city is about – toughness and grit. And that’s the way he fought this cancer.”

Safety Brian Dawkins played 10 years under Johnson with the Eagles. “He was a tough coach who wasn’t afraid to let you know how he was feeling,” Dawkins said in a statement quoted by CBSSportsline.com. “At the same time, he cared about us deeply.”

Baltimore Coach John Harbaugh: “I loved Jim Johnson. This is a sad day for so many people who were touched by this great man. … Jim was a tremendous teacher of football and life. He had a special ability to bring out the best in people while getting you to see the best in yourself. He saw potential and developed it. … For me, he was a father-type mentor and above all, a cherished friend. He belongs in the Hall of Fame. I will miss him so much.”

There are a number of coaches – head and assistant – who can make a case for the Hall. Don Coryell. Dick LeBeau. Perhaps Dick Rauch of the Pottsville Maroons. But Jim Johnson made a strong case for himself as well.

Fans of the Philadelphia Eagles should feel lucky to have had him for a decade.