Despite his history of being disciplined for illegal hits to the head, safety Brandon Meriweather (31) is expected to be a starter. (Jonathan Newton/The Washington Post)

Ask most NFL coaches to explain the key to success on defense, and you’ll likely get the same answer: a strong pass rush. For the Washington Redskins, it has never been more important.

The Redskins committed a chunk of their payroll in an effort to bolster their pass rush — outside linebacker Brian Orakpo and defensive lineman Jason Hatcher will be paid almost $22 million combined this season — but they did little to address their secondary, the weakest area of the roster. Hitting the quarterback more frequently, Redskins President and General Manager Bruce Allen believes, could do wonders for the secondary. Based on what we’ve seen, Washington’s pass rush had better be fantastic.

For years, the Redskins have been unsettled at safety. The group is proof that lack of talent and poor decision-making is an awful combination. The fact that safety Brandon Meriweather still is on the roster, let alone expected to start again, best illustrates why the Redskins must lean on the front seven even more heavily than usual.

Meriweather has a history of being disciplined for illegal hits to the head. He often plays so recklessly — Meriweather last season drew a two-game suspension for hits that violated league rules — he’s a hazard to himself as well as anyone unfortunate enough to be on the field with him. If Meriweather is one of your leaders at safety, you’re basically rudderless at the position.

Apparently, Allen realized as much, prompting him to bring back reliable veteran Ryan Clark. Steady with Washington in 2004 and 2005, Clark signed with the Pittsburgh Steelers in free agency in 2006 and spent the past eight seasons with them.

There’s no doubt Clark, entering his 13th season, will raise the level of professionalism in Washington’s locker room. It’s unclear whether he’s capable of helping significantly on the field.

To say the least, the Steelers, who did not attempt to re-sign Clark, have proven to be better than the Redskins at making successful player-personnel moves. We all lose a step — or more — with age, and the word around the league is that Clark, who turns 35 in October, no longer possesses the speed to cover well.

And even when Clark was in his prime, he wasn’t a game-changer. With future Hall of Famer Troy Polamalu often making big plays all over the field, the Steelers merely needed their other starting safety to be fundamentally sound. Clark fits the description.

Of course, if Clark takes proper angles in tackling, he’ll provide more than the Redskins got from rookie Bacarri Rambo a season ago. Listed as a starter entering training camp in 2013, Rambo had major tackling problems in the preseason. They continued during the regular season, resulting in Rambo disappearing from the team’s plans.

Fortunately for Rambo, he has a blank slate with new Coach Jay Gruden. Despite Rambo’s inability to wrap up a tackling dummy last season, “we have high hopes for him,” Gruden said Wednesday after offseason practice at Redskins Park. “He’s got great ball skills. He’s not afraid to tackle. He’s got to do a better job tackling.”

The Redskins seem willing to give Rambo another chance. Same goes for veteran Tanard Jackson.

A repeat offender of the league’s substance-abuse policy, Jackson was recently reinstated after being suspended without pay since August of 2012. He has played in only one season the past four years while serving three drug-related suspensions.

Although Jackson impressed with the Tampa Bay Buccaneers before his missteps, you could easily argue the Redskins shouldn’t waste another minute on him. Then again, with their lineup at safety, the Redskins have to pursue all options to potentially strengthen the position.

They’re hopeful Phillip Thomas will provide support.

In the 2013 preseason opener, Thomas suffered a foot injury and was sidelined his entire rookie year. The Redskins must quickly determine whether Thomas can play. “Phillip Thomas has done some good things” in offseason work, Gruden said.

Gruden expects great things from top cornerback DeAngelo Hall. After experiencing a career renassaince last fall, Hall signed a new contract and remains the undisputed leader of the the defensive backfield. He’s high on second-year corner David Amerson, who’s expected to start opposite Hall, and confident Washington’s safeties will deliver — with an assist.

“Our pass rush is going to be good — real good,” Hall told me the other day. “ ’Rak has been working as hard as he always does to be the best he can, and now you see him just adding more and more [to his pass-rushing repertoire] to go out there and just have a great year.

“And Hatch, man, Hatch . . . he’s just a beast. When you see the way he gets after [the quarterback], you’re just glad he’s on your side now.

He’s going to make a huge difference. . . . Are those guys going to help [the secondary]? You better believe they will.”

The Redskins have faith their pass rush will do a lot. Their secondary is counting on it.