Rex Grossman admittedly didn’t play his finest game last Sunday as Washington fell 34-19 to the New York Jets. But the Washington Redskins quarterback knows he must put that outing behind him.

The nine-year veteran completed just 19 of his 46 passes (just 41.3 percent, second-lowest of his season) for 221 yards and an interception, was sacked twice and fumbled once. Grossman’s struggles were a big reason why Washington’s offense regressed after solid back-to-back outings against the Cowboys and Seahawks.

“I think as he looks at the film, he’ll be somewhat disappointed in his play,” Redskins coach Mike Shanahan said earlier this week. “But that’s the nature of the quarterback position. You’ve got to be able to wipe it out and bounce back and concentrate and look for that perfect game . . . At the end of the day, a quarterback knows if he’s on or off a little bit.”

Sure enough, Grossman, who spoke to the media on Wednesday, had a clear understanding of what held him back against the Jets.

“Generally, there were some plays, normally on our field goal drives, had I made quicker decisions, we might have had four more points,” said Grossman, who after directing a game-opening touchdown drive saw his offense have to settle for four field goals the rest of the game. “Our last field goal, there might have been an attempt to move the chains, and we ended up getting a long field goal. End of the first half, I was a little late on one play — it (pass) got tipped. Those are two areas that I definitely just need to do a better job during the week of exactly how I’m going to go about running those plays with footwork so that everything times up. It was more of a fundamental footwork area that I was late to both of those plays. Those are the things you look back on when you lose as plays you can do better. When you win, those kind of get shoved under the rug.”

If Grossman can produce at a high level, and if receivers Santana Moss, Jabar Gaffney & Co. can help compensate for the loss of suspended tight end Fred Davis, the Redskins have a chance to move the ball. The Patriots’ defense ranks dead-last in the league in yards allowed, yielding slightly more than 412 yards per game.

But New England buckles down in the red zone and ranks 13th in the league in points allowed, holding foes to 20.6 points a game.

“We’ve got to be sharp,” said Grossman, who has had to study slightly more this week because the Patriots use both 3-4 and 4-3 defensive fronts to keep offenses guessing. “We have to do a real good job of moving the chains and having some long scoring drives. My mindset doesn’t really change at all rather than just understanding their basic philosophy and reacting to everything I see with a plan and not try to overcompensate for things you don’t control.”

Patriots coach Bill Belichick said despite Grossman and the Redskins’ struggles with consistency, and the quarterback’s 15 interceptions, New England’s defense doesn’t take Grossman lightly because of his aggressiveness.

“I think that’s part of what makes him good is that he is aggressive,” Belichick said. “Defensively just because it looks like you have fairly good coverage on a player doesn’t mean he won’t try to stick it in there. Sometimes he makes plays and sometimes it doesn’t quite get into that spot, but he’s definitely not afraid to be aggressive and throw it in there. I think defensively you have to respect that.”