The Redskins’ Ryan Kerrigan sacked Cowboys quarterback Dak Prescott in the fourth quarter, causing a fumble that was recovered for a touchdown. (Ricky Carioti/The Washington Post)

The celebration spilled into the front row of the FedEx Field stands as linebacker Preston Smith disappeared into a sea of teammates and fans about to taste a victory over the rival Dallas Cowboys for the first time since 2016.

Moments before, the Washington front seven continued its dominant play when Ryan Kerrigan came on a delayed rush and strip-sacked Cowboys quarterback Dak Prescott in the end zone, where Smith picked up the ball to score his first career touchdown. That put the Redskins ahead by 10 with 4:55 remaining in the fourth quarter, and Washington held on for a 20-17 victory, thanks to a 52-yard field goal attempt by Dallas kicker Brett Maher that ricocheted off the left upright.

The play was made by two of the most criticized players on the roster in Kerrigan and Smith, who entered the game with a combined sack total — one — that hasn’t painted an accurate picture of their play on the field.

“We’re always around the ball even though people, statistically, may not feel we have enough sacks or might not be a doing a good enough job rushing,” Smith said. “We’re always around the ball regardless of what they think.”

The Washington defense and the guys up front in particular have begun punishing offenses on a weekly basis. Outside of an embarrassing 43 points allowed to Drew Brees and the New Orleans Saints on “Monday Night Football,” the Redskins have yet to allow more than 21 points this season. The Green Bay Packers, Carolina Panthers and Cowboys were held to 17 points apiece.

And a casualty list of high-profile running backs is piling up.

David Johnson. Alvin Kamara. Christian McCaffrey. Now Ezekiel Elliott.

Redskins Coach Jay Gruden said Sunday was the best effort he has seen from the defensive line in 2018, going against a Cowboys offensive line known to be one of the best in the NFL for the past few years.

“You’re talking about an excellent running back,” Gruden said, “a great running quarterback, a physical quarterback, big offensive line, very, obviously, talented. And those guys kept it going.

“Not only were they stopping the run, but they had to rush the passer there nonstop at the end of the game. Did some great things, man. I’m happy as heck to see them play like that.”

The Redskins’ run defense has been a pushover the past few years, but that is no longer the case. Washington held Elliott to 33 yards on 15 carries for the second-lowest output of his career. The unit has fully established itself as one of the best run defenses in the NFL. No individual runner has hung 100 yards on the Redskins this season.

Washington employed a similar strategy to the one it used last week against the Panthers: take the running back away first, then deal with the rest.

“We want to stop the run,” linebacker Mason Foster said. “People talked about it all year about being the last rushing defense last year. We’ve got our guys back. . . . It’s big for us.

“We take that challenge head on. . . . We take it personal. You have to. We know if we control the trenches, we have a good chance of winning.”

Washington began the day ranked sixth in the league against the run, allowing just 90.2 yards per game. Last week, the Panthers abandoned the run after McCaffrey was bottled up and Cam Newton was held in relative check. A similar scene played out Sunday. The Redskins put all their focus on Elliott and dared Prescott to beat them.

“A lot of guys were around the line of scrimmage,” Cowboys Coach Jason Garrett said. “We tried to attack in a lot of different ways, and they defended it well. [We] wanted to be persistent running the football throughout. Ultimately, we had to move the ball by throwing it.”

Gruden said the team drafted defensive tackle Daron Payne with the No. 13 pick specifically for these moments — facing Elliott and the rest of the run-heavy NFC East. The run defense actually had a strong start in 2017 before first-round pick Jonathan Allen went down after five games. It ended the season last in the NFL.

The combination of Payne and Allen has given opponents trouble and clogged running lanes with regularity. Their action up front has allowed more space and freedom for the linebackers to make plays and stay in the right position.

“Everyone here hates the Cowboys, so whenever you get a chance to beat them, it’s always big for this organization,” Allen said. “I’ve been telling Preston, ‘Just keep chopping the wood. The big plays are going to come.’ ”

An enormous one came Sunday, and now the Redskins sit alone in first place atop the NFC East.