Vikings quarterback Sam Bradford (8) was sacked three times Sunday at FedEx Field, including twice on Minnesota’s final drive. (Patrick Semansky/Associated Press)

The unraveling of the Minnesota Vikings’ season continued Sunday at FedEx Field.

The Vikings, once the league’s most surprising success story with their 5-0 start, have become the team they probably should have been all along after losing quarterback Teddy Bridgewater, tailback Adrian Pederson and left tackle Matt Kalil to major injuries.

Their fourth straight loss was delivered Sunday by the Washington Redskins, 26-20. The Vikings wiped out an early two-touchdown deficit to lead at halftime. But yet another missed extra point by place kicker Blair Walsh with no time remaining in the first half was an ominous sign, and the Minnesota offense stalled in the second half.

“We’ve got to figure out a way,” defensive end Brian Robison said. “At the end of day, we’ve got to go back to work this week and figure out what it is that we’ve got to do in order to be able to pull out these close games that we tend to be losing. We’re in a slump right now. So we’ve got to make sure that we find a way to get ourselves out of it.”

Quarterback Sam Bradford had a mostly efficient day for the Vikings, completing 31 of 40 passes for 307 yards and two touchdowns. But he also threw a fourth-quarter interception to Redskins linebacker Preston Smith, who made a dazzling play while dropping into coverage. Bradford was sacked on fourth down in the game’s final seconds to thwart Minnesota’s last-gasp effort for a winning touchdown.

The Vikings also lost another offensive lineman as Jake Long, their most recent starter at left tackle, suffered what Coach Mike Zimmer said was an Achilles’ injury. Long’s injury is believed to be season-ending, Zimmer said.

“I’m concerned, obviously,” Zimmer said. “But I still believe. We need to do a couple things here and a couple things there and we can win games. … I just feel like if we can get over the hump, if we can just keep fighting until we do that, positive things will happen. It doesn’t look like that right now. But the big thing is if we don’t have fight, we have no chance. We have guys that are fighting. We just aren’t playing well enough right now.”

Wide receiver Stefon Diggs had a superb performance in his homecoming. The former Good Counsel High School and University of Maryland standout had 13 catches for 164 yards with a group of family members in attendance. But it wasn’t enough for the Vikings to get back into the win column.

“It hurt a little bit, you know, because that’s my family,” Diggs said. “I want to win for them and I want to win for the team. I want to do everything I can to help this team. So it’s just back to the drawing board, continue to scrap, continue to work hard. You could tell it hurt a little bit.”

The Vikings couldn’t generate much of a running game on offense and couldn’t make the key plays in crunch time. Not only have they dropped out of the running to be the NFC’s best team, it has become highly questionable whether they can put things back together and reach the playoffs.

The offense has changed in two games since Norv Turner abruptly resigned as coordinator and was replaced by Pat Shurmur. The offensive line is not being exploited as badly, and Bradford is getting the football out of his hand rapidly with short, quick-hitting passes. But that has yet to translate into a victory.

The usually powerful Vikings defense played down to the level of the Minnesota offense in the early going Sunday as the Redskins sprinted to a 14-0 lead. Two Vikings defenders collided to prevent a potential interception just before the Redskins’ opening touchdown. Redskins quarterback Kirk Cousins had his choice of wide-open receivers on Washington’s second touchdown. Cousins threw to tight end Vernon Davis. But wide receiver Pierre Garcon also was running free in the secondary.

The Vikings didn’t quit. They fought back for three first-half touchdowns, the last one on a three-yard pass from Bradford to wideout Adam Thielen as time expired in the first half. But Walsh missed his fourth extra point of the season, perhaps ending his career with the Vikings. The team held kicker workouts last week but stuck with Walsh, who also has four missed field goals this season.

“Honestly I didn’t even see the kick,” Zimmer said. “So I don’t know what happened on it other than he missed.”

The Vikings failed to score after halftime, and the Redskins got four second-half field goals from Dustin Hopkins.

Zimmer’s postgame news conference ended with him being asked what makes him believe that his team can regroup, especially with the injuries continuing to pile up.

“We have no choice,” he said. “That’s what we have to do.”