Washington Redskins quarterback Robert Griffin III is remaining steady despite the loss of key playmakers, the struggles of his defense and the daunting task of winning in Pittsburgh. (Tyson Trish/Associated Press/Bergen County Record)

When they formulated their plans for this season, Washington Redskins brass aimed to ease the pressure on rookie quarterback Robert Griffin III by surrounding him with weapons on offense and a formidable defense.

Seven games into the season, however, circumstances are rather different, to say the least.

Guilty of poor execution primarily on big pass plays, the Redskins’ defense ranks among the worst in the league statistically. Washington has surrendered seven pass plays of 40 yards or more, tied for first in the NFL.

On offense, the Redskins haven’t had explosive wide receiver Pierre Garcon at full strength since he hobbled off the field eight plays into the season opener at New Orleans. On Sunday, Garcon missed his fourth game, and the team’s only remaining big-play pass catcher, tight end Fred Davis, was lost for the season when he ruptured his left Achilles’ tendon early in the 27-23 loss to the New York Giants.

As a result, Griffin has been anything but a game manager. He is passing for 229 yards per contest, with a league-best 70.4 percent completion rate, and rushing for 66.9 yards per outing.

The Redskins are preparing to play the Steelers on Sunday at Heinz Field, where Pittsburgh has won nine of its past 10 regular season games. With Steelers quarterback Ben Roethlisberger putting up career passing numbers and Washington’s cache of offensive weapons reduced, the Redskins are expected to lean heavily on Griffin again.

Griffin insists that he doesn’t feel additional pressure given the state of his 3-4 team. He said he’ll attack the Steelers with the same balance of aggression and patience he has strived for in each game.

“I don’t feel that burden,” Griffin said Wednesday. “The guys have come to me numerous times and told me, don’t feel like I have to do more than what I’m doing right now. I just go out there and continue to execute the offense, do what the coaches say, and everyone will step up.

“We can’t replace Pierre or Fred,” Griffin added. “They’re two unique individuals, and unique players. You’ve got to find guys that will step up and play with you.”

The Redskins are trying to determine who is capable of coming to Griffin’s aid.

Rookie running back Alfred Morris is doing his share. With 658 rushing yards (4.8 per carry), he trails Houston’s Arian Foster for the league lead by one yard.

But none of the members of the receiving corps has performed consistently. Sunday’s six-catch, 70-yard outing by second-year pro Leonard Hankerson was his most active day of the season, and veteran Josh Morgan — signed in the offseason to complement Garcon — has averaged only 2.5 catches and 31 yards per game.

Hankerson said he is ready to build on last week’s performance.

“This is what I’m here for, and why I’m a Washington Redskin — to make plays,” the 2011 third-round pick said. “We do it every day in practice, and we have to do it now. We’re all confident.”

The Redskins also will count on third-year tight end Logan Paulsen (four catches, 76 yards last week) and re-signed tight end Chris Cooley to produce as pass catchers and blockers.

Redskins Coach Mike Shanahan said the team needs all those players to step up, but he is confident that Griffin can continue to fuel the team’s efforts.

If Griffin has felt the pressure, “he’s handled it pretty good, don’t you think?” Shanahan said. “That’s all you can ask. He’s handled it as well as a rookie could handle it: scoring some points, not making many mistakes, and you just hope he can continue to play at that level.”

Griffin’s counterpart on Sunday, Roethlisberger, won 2004 rookie of the year honors and helped the Steelers to the AFC championship game. But Roethlisberger said that Griffin is in a much different situation.

“He’s putting up a lot better numbers than I did my rookie year. . . . I played on a very good team that I just had to go out and try and just win games and didn’t have to try to put up big numbers,” Roethlisberger said. The Steelers boasted the top defense and second-best rushing attack in the league that season, and asked Roethlisberger to simply manage games as a rookie. “He’s doing some amazing things.”

Said Pittsburgh Coach Mike Tomlin of Griffin: “He’s a special talent, not only in terms of what he can do with his arms, but also his legs. . . . But bigger than the physical talent, it’s obvious that the stage isn’t too big for him. . . . He appears to be extremely comfortable while executing.”

Griffin said he focuses on not trying to do too much, but relishes the opportunity to make plays. In two of the Redskins’ threevictories, Griffin has orchestrated game-clinching drives. He has been in position to direct game-winning drives three other times before penalties (twice) and a fumble (against New York) foiled Washington’s efforts.

“I would love to go out and dominate a team and put them away early and be able to sit on the sidelines and eat some popcorn or something,” Griffin said. “But if you are in that situation and you’re down, or you’re up and you’ve got to stay on the field to run the clock out, you do relish those situations, because you want the ball in your hands in crunch time, and you do want to show everybody that you can lead your team down the field. Sometimes it happens, sometimes it doesn’t, but for the most part, you believe that you will.”