PHILADELPHIA -- New Philadelphia Eagles defensive coordinator Sean McDermott has learned too much from Jim Johnson -- in life and football -- to discuss in one news conference.

"What haven't I learned from Jim?" McDermott said Saturday upon being introduced as Johnson's replacement. "I don't think it would be fair to Jim, in this setting, to try and limit in one statement, one press conference, the effect that Jim has had on my life."

After spending the last eight seasons as a defensive assistant under Johnson, McDermott on Friday was named to succeed his mentor.

Johnson, the only defensive coordinator the Eagles have had since Andy Reid became coach in 1999, took an indefinite leave of absence in May to continue treatment for a cancerous tumor on his spine. It's uncertain whether he'll return to the team in any capacity.

"This seat is an important and respected seat that I'm sitting in right now," McDermott said. "It's important to understand that some of my biggest concerns right now are for Jim, his wife, Vicky, and their entire family."

McDermott first joined the Eagles in 1998 as a scouting administrative assistant. He spent two seasons as an assistant to the head coach before joining the defensive coaching staff.

"He just gives you that confidence that he's got it under control," Reid said.

Widely regarded as one of the top defensive masterminds in the game, Johnson is known for his aggressive, attacking style, and his defenses have played a major role in the Eagles' success over the last decade. Last season, in advancing to their fifth NFC title game this decade, the Eagles finished third in total defense and fourth in points allowed.

"There is one thing I know, and that is that this system, it works," McDermott said. "Jim has spent a considerable amount of time in his coaching career researching and finding things that work and finding things that didn't work, quite frankly, and I'm going to respect that and we're going to build on that. From there we'll add wrinkles."

Johnson's units have been known for their ability to pressure the quarterback. Since 2000, the Eagles are second in the league in sacks with 390.

McDermott didn't hesitate when asked the most important advice he's received from Johnson.

"Blitz, and blitz again," McDermott said.

Before becoming the interim defensive coordinator in May, McDermott had been the Eagles' secondary coach. Assuming those responsibilities will be Brian Stewart, who spent the last two seasons as the Cowboys' defensive coordinator, and former Eagles safety Michael Zordich.