Cardinals coach Bruce Arians said it starts with Chargers quarterback Philip Rivers, then spreads to a unit that features talented receivers and a trio of tough running backs.
''They have multiple weapons,'' Arians said after Thursday's practice. ''Hopefully, the crowd noise will help us and we'll feed off the energy of our crowd.''
Arizona was sixth in the NFL in overall defense and first in run defense a year ago. But the heart of that defense, inside linebackers Karlos Dansby and Daryl Washington, is gone. So is defensive tackle Darnell Dockett, who went down with a season-ending knee injury in training camp.
Their replacements will, first of all, work to shut down the San Diego running game.
''They do a good job running the ball,'' said defensive end Calais Campbell, surely bound to see double teams, clearing the way for others to make the play.
''They do a good job getting the ball out quick in the passing game,'' Campbell said. ''The biggest thing is stopping the run and make it third and long so they can't nickel and dime us down the field.''
Larry Foote, a 13-year NFL veteran signed as a free agent, joins second-year pro Kevin Minter as the new inside linebackers. Frostee Rucker, who played in all 16 games for Arizona last season, moves in to the starting tackle role.
There are questions, too, at outside linebacker.
The only proven pass rusher among them is John Abraham, who was a late arrival to camp after dealing with the aftermath of his drunk driving arrest.
While the front seven was the strength of last year's defense, the secondary could be this year.
All-Pro Patrick Peterson, with a fat new contract, is joined by free agent signee Antonio Cromartie at cornerback. Jerraud Powers, who started all 16 games last year, will see a lot of time at the position, too.
At safety, the Cardinals have Rashad Johnson, surprising second-year pro Tony Jefferson and first-round draft pick Deone Bucannon. That's not counting Tyrann Mathieu, who will be back sometime early in the season after a severe knee injury cut short his spectacular rookie season.
It appears unlikely Mathieu will be able to go in the opener.
He tackled for the first time on Wednesday, and the rust showed.
''He tackled about four or five times, tackled two or three and missed four,'' Arians said, ''so it's new to him again.''
Arians' math doesn't quite add up, but the point was Mathieu didn't look ready to play.
Asked if there was a chance Mathieu could go Monday, Arians said ''We'll just continue where we're at.''
Mathieu said he just needs lots of reps, ''doing it every day,'' and wouldn't offer a guess as to when he would come back.
''I'm just trying to do my part,'' he said. ''I'm trying to leave all that up to the training staff.''
Even without Mathieu, the secondary should present a formidable challenge to Rivers and his receivers. It is, ''the strength of our defense,'' Johnson said.
The Chargers have plenty of players to test it.
''They've got a lot of skillful guys in the right positions,'' Johnson said, ''a very skillful team and it's going to be a challenge for us to come out and be the dominant defense we want to be.''
No one will be tested more than the cornerbacks.
When Arizona packs the middle to stop the zone, they often will be left on their own, ''which we are used to doing,''' Peterson said.
''He (Rivers) is going to take his shots,'' Peterson said. ''We don't know when he's going to take his shots but at some point of time in the game, if we're so insisting on stopping the run, they're going to take a shot deep.''
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