Even in success, failure often finds the Redskins. For so long now, they’ve been defined by disappointment. It’s as much a part of them as their uniforms.

Despite performing well in stretches Sunday during its most entertaining game of the season, Washington again found ways to lose, 34-27 to the New England Patriots at FedEx Field.

For a change, the Redskins were actually impressive on offense, producing a season-high in total net yards. They remained committed to the running game (another rare occurrence) and got another fine outing from rookie running back Roy Helu.

The Redskins also scored a long touchdown on a nifty trick play. They did a lot right in pushing the AFC East-leading Patriots in a game that was fun to watch.

Yet the end result was Washington’s eighth loss in nine games. The Redskins will miss the playoffs for the fourth consecutive season and the ninth time in Daniel Snyder’s 12 years as owner.

That became official when Santana Moss couldn’t come up with Rex Grossman’s final pass and the ball caromed off Moss toward New England linebacker Jerod Mayo, who made a diving, game-clinching interception.

At the New England 9-yard line and driving to tie the score or win the game with a touchdown and a two-point conversion in the final 30 seconds, Washington instead was mathematically eliminated from postseason contention.

From a potential upbeat moment in another dreary season to an awful experience in the blink of an eye. “I don’t know why it keeps happening,” inside linebacker London Fletcher said. “In this game, it always comes down to whichever team makes the most plays, and we made a lot. But you have to make enough. A lot of times, we just don’t do that.”

Grossman isn’t in the same league (universe?) with Patriots quarterback Tom Brady. No right-minded person would argue that one. On Sunday, though, Grossman matched up favorably with the future Hall of Famer. Grossman again displayed his big-play ability, which was a key factor in the score being tied, 20-20, at halftime.

Unfortunately, as is usually the case with Grossman, he contributed to both the Redskins and their opponent.

Early in the first quarter, former Redskins defensive end Andre Carter forced a fumble while sacking Grossman in the end zone. Defensive tackle Vince Wilfork recovered the ball in the end zone to help New England take a quick 7-0 lead.

Grossman had two touchdown passes while directing an offense that amassed 463 yards. He made a lot of nice throws to extend drives. Granted, New England’s defense is awful. It offered little resistance. The Patriots rank last in the NFL in yards allowed, and they have truly earned their position. But Grossman had many good moments.

His six-point fumble, however, was exactly the type of thing that continues to plague the Redskins. It holds them back from returning to what they once were, or at least something close to it.

Return specialist Brandon Banks and Moss combined on a 49-yard touchdown pass on a trick play. Smartly, Shanahan and his offensive coordinator son, Kyle, continued to feed Helu, who had 27 rushes for 126 yards (a 4.7-yard average) and became the first Redskins rookie running back with three straight 100-yard games. Washington dominated in time of possession.

Grossman’s early fumble cost them a lot. If that kind of stuff doesn’t stop, Shanahan won’t have any chance here.

Shanahan also needs all of his team’s leaders to truly lead. Cornerback DeAngelo Hall made another wrong turn in his uneven season.

On New England tight end Rob Gronkowski’s spectacular 49-yard reception in the first quarter, Hall, Washington’s co-captain on defense, incorrectly presumed the play was over.

Hall did not help safeties Reed Doughty and DeJon Gomes bring down the imposing second-year player, listed at 6 feet 6 and 265 pounds. Instead, he walked away from the sideline as they tried to corral him.

Bouncing off tacklers as if he were in a pinball game, Gronkowski rambled to the 11-yard line. He caught a touchdown pass from Brady on the next play.

“I thought he stepped out,” Hall said.

Hall’s teammates defended his inaction.

“That happens,” Doughty said. “You always wanna hustle, but at the same time, I thought he stepped out of bounds. I was right there.”

Said Fletcher, who shares captain duties with Hall: “The way the league is now, you worry about a late-hit penalty [along the sideline]. I’m sure that’s what D was thinking right there.”

Hall and the Redskins offered no excuses for his big mental blunder in the third.

Called for holding on Patriots slot receiver Wes Welker, Hall picked up the official’s flag and tossed it. In addition to the five-yard holding penalty, Hall was assessed a 15-yard unsportsmanlike penalty for his flag toss. The possession ended with Brady and Gronkowski teaming on a 37-yard touchdown.

Although Hall knows he erred, you just can’t have that. Especially in the first week left tackle Trent Williams, a co-captain on offense, and tight end Fred Davis, Washington’s top player in the passing game, began serving season-ending suspensions for violating the league’s substance-abuse policy.

Each week, the Redskins’ offseason to-do list grows. There’s still so much work ahead. Somehow, they’ve got to start to break this bad cycle. It’s way past time.