Hiring a head coach isn’t just about hiring a head coach; it’s also about whom that head coach brings with him. Sometimes those hidden hires are the difference between winning and losing.

Late in 2019, not long after Ron Rivera met with Washington Football Team owner Daniel Snyder for a third time, he got a call from Jack Del Rio, who was looking for a job. Rivera was intrigued. They had never worked together, but they had a lot in common as longtime head coaches in their late 50s who like fierce, aggressive defense, and they had even been all-American linebackers just a year apart in what used to be known as the Pac-10 Conference.

It had been almost two years since Del Rio had been fired as the Oakland Raiders’ head coach, and he wanted back in the league. Rivera, who was close to landing the job in Washington, needed someone to lead his defense, so he flew to Destin, Fla., where Del Rio lived. They quickly realized they shared many defensive philosophies.

“Everything that he said, I believed in,” Rivera recalled this week. “That made it really simple for me.”

When Rivera took the Washington job a few weeks later, Del Rio was his first hire.

So many stories have swirled around Washington this season, from its name change to Rivera’s battle with cancer to quarterback Alex Smith’s return from a life-threatening leg injury and the rise of star rookie Chase Young, that Del Rio’s impact as defensive coordinator has been lost in the churn. And yet it’s hard to imagine Washington winning the NFC East without him. In a year without a normal offseason, with limited meeting time and fewer chances than normal to install a new scheme, Del Rio has turned a defense that was near the bottom of the NFL in most categories in 2019 into one that was fourth in yards allowed and second in points given up in 2020.

Some of this is Young, who could be the NFL’s defensive rookie of the year. And some of this is a remade secondary and guidance from Rivera, who pushed a new culture and a sense of accountability. But a lot of this is Del Rio, who brought with him a 4-3 defense that best fits the team’s biggest strength — a defensive line filled with first-round draft picks — and encouraged his players to besiege the quarterback and hit harder than they had before.

“The biggest thing, of course, [is] Jack being a great addition,” defensive end Montez Sweat said Sunday night after Washington’s division-clinching victory in Philadelphia.

Perhaps no player made a bigger transition under Del Rio than Sweat, who turned in nine sacks and two forced fumbles after an inconsistent rookie season in 2019. But others have thrived, too, such as defensive tackles Jonathan Allen and Daron Payne, who were freed to rush the passer.

Del Rio has built the kind of physical, intimidating defense that Tampa Bay quarterback Tom Brady hates to face — one that can get to the quarterback and knock him down. If Washington is going to pull an upset few expect Saturday night at FedEx Field, 7-9 beating 11-5, it’s going to be Del Rio’s pass rush that makes it happen.

And that’s why it’s sometimes not just a new head coach who makes the difference for a franchise but the hires that coach makes. Six teams are searching for coaches this week, with a blizzard of names rumored for each. Early in the interviews for those jobs, the candidates will be asked an essential question: “Who would your top assistants be?” For the people doing the hiring, the answer can mean everything. The wrong coordinators running the wrong schemes can doom an entire regime.

One of the biggest reasons Rivera wanted to talk to Del Rio was a mistake Rivera had made years before, in his first season as a head coach. None of the assistants he hired on his Carolina Panthers staff in 2011 had been a head coach, which became an issue as the year unfolded and Rivera realized he had no one to ask what to do when things went wrong. After that, he vowed to always have a former head coach on his staff.

Del Rio had spent a dozen years as the head coach of the Jacksonville Jaguars and Raiders, coaching 187 games, including four in the postseason. There was nothing he hadn’t seen. “We want to share ideas,” Del Rio said, not long after he had been hired by Washington, of his partnership with Rivera.

Neither knew how much that would matter until August, when Rivera was diagnosed with cancer. He coached through treatment that sometimes left him barely able to stand and forced him away from meetings and planning sessions he would normally run.

“I really had to step away from meddling,” he said this week.

Del Rio became almost a second head coach at times, the one who had to keep the team running when Rivera was resting or receiving treatment. Without a decent bond, this season could have been a disaster. Had they not decided, when they met in Destin in December 2019, exactly what they wanted this defense to become, they probably wouldn’t be building a playoff game plan around one of the league’s best defenses this week.

“He’ll either suggest something and we’ll talk about it, or I’ll go up to him and I’ll say: ‘Hey, I was thinking about this. What do you think?’ ” Rivera said. “And he’ll either agree or disagree, and he’ll give me reasons why.

“A lot of times people will say, ‘Whatever you want to do, Coach.’ Jack will say: ‘No, how about this, Coach? You’re right about this. I don’t like this because of this.’ At least I’ll have somebody with some input and somebody with some insight.”

This week, Rivera chuckled about Del Rio’s tweets in support of President Trump, calling them “a brouhaha” before adding, “But that’s who he is; he’s not going to change who he is.”

Rivera was careful to offer neither an endorsement nor a condemnation of Del Rio’s Twitter activity. The point he was making was that Del Rio remains true to his beliefs, in politics or in football. And at a time when Rivera needed a defensive coordinator unafraid to be himself, he is happy to have made the right hidden hire at the right time, which is something a lot of coaches continue to get wrong.