Whenever he encounters struggles or falls short in an assignment, Washington Redskins left tackle Trent Williams takes a simple approach.

“Just wipe it out,” he reminds himself and then moves onto the next play.

As his downtrodden Redskins put the finishing touches on their game plan for the New York Giants, who will visit FedEx Field on Sunday night, Williams will attempt to wipe it out again. But he is trying to move on from more than just one poor play.

In the last month, Williams hasn’t looked like the rock-solid tackle that anchored the Redskins’ line last season, helping his team win the NFC East and earning his first Pro Bowl selection.

After a strong start to this season, when he went six straight weeks without allowing a sack, Williams has given up six in the last five games. Then his image took a hit last week when he found himself at the center of controversy following an alleged profanity-laced exchange with a referee.

Two weeks ago, following the Redskins’ loss at Philadelphia, Williams seethed in the locker room and revealed that referee Roy Ellison verbally abused him. Williams said Ellison called him a “garbage [expletive], disrespectful [expletive].”

Ellison received a one-game suspension from the NFL, but the official reported to the Fritz Pollard Alliance that Williams had used abusive language and directed a racial epithet at Ellison after the official tried to break up a fight between Williams and several Eagles players. Williams, who was not disciplined by the NFL, denied using any derogatory language toward Ellison.

The matter seemingly had been laid to rest by the end of last week when Ellison’s suspension was handed down, and Williams said he had moved on.

But he couldn’t work his way out of his on-field funk.

The Redskins hosted the San Francisco 49ers in what represented a must-win game on “Monday Night Football.” But Williams had the worst game of his season — and arguably one of the worst of his career — as he surrendered two sacks to defensive end Aldon Smith. The No. 4 overall pick of the 2010 draft also surrendered another four quarterback pressures, and Robert Griffin III and the Redskins’ offense failed to score a touchdown for the first time in the last two seasons.

“Yeah, Trent had a tough game,” Redskins Coach Mike Shanahan said. “He didn’t have one of his better games [Monday]. He played against a couple of pretty good players, too. He gave some great effort but didn’t have one of his better games. We didn’t play like we normally play with the offensive line. It wasn’t one of our better games, and for us to win, we have to play better.”

Said offensive coordinator Kyle Shanahan: “Aldon Smith is a very good player, probably the best [Williams has] seen this year, so he obviously needed to be at his best versus him to have a solid game, and I think he knows he wasn’t. Any time you have a few bad plays like that, they’re crushing because he’s going to get after the quarterback. But all you can do is get past that game, and hopefully he comes back better and plays better.”

For Williams, it marked the second time since Washington’s game at Denver in Week 8 that he had surrendered two sacks in one game. He had not yielded two sacks in a game since Week 1 of the 2011 campaign and allowed only four sacks all last season.

Williams initially took the poor performance hard.

“Me, personally, giving up a sack, I feel like the whole game is messed up,” he said.

But as he tries to put Monday’s outing far from his memory, he also looks on the bright side.

“Looking back on it, how many times did we throw the ball, almost 30 times?” he asked. “Any time you block a guy 30 times, it’s not always going to be perfect. He’s a great, great pass-rusher. He’s pretty damn good. You look back, and nothing is quite as bad as it seemed at the time.”

Williams said the Ellison incident didn’t serve as a distraction for him. “It was nothing to block out for me.”

Meanwhile, he’s not counting on a carry-over from the 49ers game or the struggles in three of four previous outings.

“I’ve wiped it out,” he said. “Have to. You’re a competitor. Any time you get beat, you’re going to feel a certain way. But you have to wipe it out.”

With the Redskins owners of a 3-8 record, it appears unlikely Williams and his teammates will make a second straight playoff appearance. In fact, with a loss to the Giants on Sunday, Washington will be officially eliminated from contention.

The disappointing finish also means Williams appears unlikely to return to the Pro Bowl this season.

The personal accolade is a non-factor, Williams says. But he aims to elevate his play and lead his teammates to a respectable finish.

“Nobody’s thinking about quitting,” said Williams, who is a co-captain of the offense. “We still have some good that we can make of this season — 8-8, in this division where everybody has at least five losses. You never know how things will shake out. It doesn’t look promising, but you still have to run the race.”