Within hours of becoming the coach of the Washington Redskins, Ron Rivera made his first big hire, adding former Jacksonville Jaguars and Oakland Raiders head coach Jack Del Rio as defensive coordinator.

The combination of Rivera and Del Rio puts two of the league’s best defensive minds at the top of the team’s coaching staff, showing the Redskins probably are committed to building around a defense that is filled with promising players in their mid-20s or younger.

“These are two old school linebackers that can speak the same language with each other,” Fox NFL analyst Charles Davis said. “Ron will not have to worry about coordinating the defense as the head coach, which he had to do, really, for the last year and a half in Carolina.”

In confirming his hire Wednesday morning, Del Rio said he will run a 4-3 defense — a dramatic change from the 3-4 scheme Washington had been using. The new scheme should emphasize one of Washington’s biggest strengths — a group of gifted defensive linemen that includes recent first-round picks Jonathan Allen and Daron Payne, as well as rising star Matt Ioannidis and Tim Settle, who played well last season. Pass rusher Montez Sweat, a first-round pick last spring, also could benefit from the new defense, as might Ryan Kerrigan, whose statistics declined last season.

While a 4-3 should decrease the times pass rushers such as Sweat and Kerrigan are dropped into coverage, the specifics of the subpackages will have a heavy influence. Davis noted teams are out of their base defense much of the time.

Del Rio was the first of what may be many big moves made by Rivera and team owner Daniel Snyder. Multiple reports said Rivera is interested in keeping current offensive coordinator Kevin O’Connell. While O’Connell called plays for the first time after former head coach Jay Gruden was let go in early October, he is well regarded around the league and might have other opportunities. He seemed to build a strong relationship with rookie quarterback Dwayne Haskins, something Rivera might want to maintain.

It was unclear how many of the other Redskins assistants, if any, Rivera will keep. Interim coach Bill Callahan, who had coached the offensive line before Gruden’s firing, was let go Wednesday. The fate of others was uncertain. NBC Sports Washington reported Wednesday that O’Connell, running backs coach Randy Jordan and special teams coordinator Nate Kaczsor were among a small group under consideration for jobs on Rivera’s staff.

For now, it appears the defense is Rivera’s biggest target for improvement.

Many coaches and talent evaluators around the NFL have wondered over the past two seasons why previous defensive coordinator Greg Manusky kept running a 3-4, believing the players on the Redskins’ defense better fit a 4-3. The Redskins were 27th in the NFL in yards allowed this past season and 15th the season before.

“They’re playing the wrong defense. That unit is way too good,” said one NFL assistant coach, who spoke on the condition of anonymity because he was talking about another team.

Allen, a player who stands to benefit most from the new scheme, said he was excited about the new defense but cautioned that it will take some time to learn the system.

“We haven’t played in it in the last three years,” Allen said Wednesday. “Going back to college, me and Payne [Allen’s teammate at Alabama] haven’t played in it since high school, pretty much. So it’s definitely going to take a little bit of an adjustment period, but I’m very optimistic and I have a good feeling about what switching to a 4-3 can do for us.

“Anytime you go from a 3-4 to a 4-3, it allows the defensive line to have more opportunities to make plays in the backfield. So that’s kind of the biggest thing,” Allen added.

Del Rio, who was a consensus all-American linebacker at USC — just like Rivera was at California — has twice been a defensive coordinator: in 2002 with Carolina and from 2012 to 2014 with Denver. Three of the four defenses were second or third in the league in fewest yards allowed. As a head coach, he helped rebuild teams at Jacksonville and Oakland, leading both to the playoffs soon after taking over. He was 93-94 in nearly 12 seasons as a head coach.

“For Ron, this is another professional you don’t have to worry about,” Davis said. “Jack Del Rio walks through that door, and kids may not know as much about him, but they will immediately sense that they should. It won’t take long for it to get around. …

“This is another legit guy. I don’t want to go all ‘Goodfellas,' but he’s a made man,” he continued. “For a team that’s trying to get on its feet, to have that kind of professionalism walk through the door and present itself every day, it’s a big deal.”

Mark Maske contributed to this report.

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