Vikings wide receiver Adam Thielen (19) caught eight passes for 166 yards and a touchdown in Sunday’s win over the Redskins. (Ricky Carioti/The Washington Post)

The 2017 Washington Redskins have had nine games to assert an identity. And the best that can be said in the wake of Sunday’s 38-30 loss to the Minnesota Vikings is that they’re maddeningly inconsistent.

One week after proving themselves a dangerous upstart capable of toppling the division-leading Seattle Seahawks, the Redskins returned to FedEx Field, where a partisan home crowd of 74,476 and a fast start were in their favor, and showed they’re equally capable of making it all too easy for opponents.

A defense that had been so stout in the upset at Seattle surrendered enough big plays to make a Pro Bowl case for Vikings third-string quarterback Case Keenum, who completed 21 of 29 passes for 304 yards and a career-high four touchdowns.

Vikings receivers torched the Redskins’ secondary, helping Minnesota score touchdowns in all five forays inside the red zone and spurring a celebratory game of leapfrog in the end zone that drew jeers from the crowd.

“We came out flat,” Redskins cornerback Bashaud Breeland said bluntly. “We came out flat; they came with energy.”

Said a frustrated Ryan Kerrigan: “It’s like you’re watching two different teams. We go out there in Seattle and play 89 plays and give up 12 points, and this week we give up 28 before the half. . . . We’ve got to find some sort of consistency and be able to make those types of performances like we had against Seattle a weekly thing. . . . Our offense scored 30 points, and that should be more than enough to win a football game.”

The loss dropped the Redskins to 4-5 heading into next week’s game at NFC South-leading New Orleans (7-2). But the fault wasn’t the defense’s alone.

The offense left far too many points unscored, coming away with touchdowns just twice in four trips inside the 20.

After letting a 17-14 lead turn into an 18-point deficit in a disastrous five-minute span to close the first half, the Redskins clawed back, spurred by safety D.J. Swearinger’s two second-half interceptions, to make it a one-score game.

Unlike last week, Cousins couldn’t conjure the heroics to complete the comeback. He struggled to complete throws inside the 20, and his wide receivers didn’t help, with Josh Doctson stumbling on one would-be touchdown and Jamison Crowder unable to hang on for another.

Cousins’s second-quarter interception — the result of a poor, high throw intended for Crowder — turned the momentum. He finished 26 for 45 for 327 yards, one touchdown and the one interception, while rushing for two scores.

The Vikings (7-2) entered the game rested, coming off their bye week, while the Redskins had muddled through yet another week of practice with a half-dozen starters limited by injury.

They got good news before kickoff. Minnesota defensive end Everson Griffen, who leads the team with 10 sacks, was ruled inactive with injury. And the Redskins’ banged-up starting offensive line returned full force for the first time in three weeks, sloughing off a litany of shoulder, knee and ankle injuries in hopes of giving Washington a chance to pull off a second consecutive upset of an NFC division leader.

Afterward, each lineman moved slowly and gingerly in the locker room, as if each step were a burden. But their protection and presence had made a difference. Cousins was sacked just once, compared with six times the previous week, and Redskins backs gained 81 yards against the NFL’s third-ranked rushing defense.

The game started favorably for the Redskins.

They breezed down the field on their opening drive and capped the series with a terrific, one-handed, 36-yard touchdown catch by Maurice Harris, who had been elevated from the practice squad just 24 hours earlier.

The Vikings responded quickly, with Keenum hitting wide receiver Stefon Diggs, a standout at Good Counsel and Maryland, for the first of several deep throws. Running back Latavius Murray carried the final yard to knot it at 7.

After the teams traded punts, the Vikings’ defense stepped up the intensity, bulldozing Cousins on one play and ending running back Rob Kelley’s day with a knee-wrenching tackle on another. After three failed attempts to score from the 10, the Redskins retook the lead at 10-7 on kicker Nick Rose’s 28-yard field goal.

The Vikings took their first lead at 14-10 on Keenum’s three-yard strike to Diggs.

The Redskins responded with a gutsy seven-minute drive that included a fourth-and-one gamble by Coach Jay Gruden. Struggling again with goal-line throws, Cousins plunged the final yard for the score, with help from linebacker Ryan Anderson masquerading as a fullback, to retake the lead at 17-14.

The momentum shifted for good in the 4:37 that remained in the second quarter. Keenum fired completions of 38 and 17 before a seven-yard scoring strike to wide receiver Adam Thielen (eight catches, 166 yards), who was barely inconvenienced by the Redskins’ secondary, for Minnesota’s third first-half score.

With his team trailing 21-17 with 1:49 to work with, Cousins threw high to Crowder, but the ball was tipped and intercepted by Mackensie Alexander. Three plays later, Keenum threw a one-yard touchdown to backup tight end David Morgan, unguarded in the end zone, sending the Vikings to the break with a 28-17 lead.

Swearinger’s second-half interceptions gave the Redskins hope. But the Vikings, who led 35-20 at that point, never let the Redskins get closer than eight points.