Last Thanksgiving, Cowboys running back Ezekiel Elliott ran over the Redskins for 121 yards. Washington can't let him get that free Sunday. (Ricky Carioti/The Washington Post)

After an enormous second-half collapse at Philadelphia in Week 1, the Washington Redskins need a victory at home Sunday to keep their season from an early downward spiral. The problem: They face their other top NFC East rival, the defending division champion Dallas Cowboys, who trampled the New York Giants in their season opener.

Washington goes into this game a big underdog, which makes sense based on Week 1’s second half; an offensive line trying to pull itself together; injuries on defense and to running back Derrius Guice (who was placed on injured reserve on Friday) and tight end Jordan Reed; and the fact that Dallas did a great job of controlling both sides of the line against New York.

Here are five keys for the Redskins against the Cowboys, who are 7-3 against Washington in Jay Gruden’s tenure as the Redskins’ coach:

Force turnovers

For much of last season, the Redskins held a sizable turnover advantage. It was a key reason they jumped to a 6-3 start and were leading the NFC East before quarterback Alex Smith broke his leg. Last Sunday, neither Washington nor Philadelphia was able to force a turnover. After the game, Coach Jay Gruden complained that the defense’s inability to take the ball away kept the Eagles on the field for long, clock-consuming drives.

Several of the Redskins’ players and coaches talked this week about an emphasis on getting turnovers. Given the way Dallas’s offensive line can control the game, the Redskins need to force quarterback Dak Prescott to make mistakes. The absence of defensive lineman Jonathan Allen won’t help matters there.

Keep letting the young receivers fly

Last week, rookie wide receiver Terry McLaurin debuted with five catches for 125 yards, including a 69-yard touchdown. The coaches were so excited about McLaurin this summer that they made him a starter and cut 2016 first-round pick Josh Doctson. They hid McLaurin for most of the preseason, but the Cowboys won’t be as surprised by him as the Eagles were.

With tight end Jordan Reed, the team’s top pass-catching threat, out again with a concussion, McLaurin and the other young wideouts — Trey Quinn and Kelvin Harmon — will become even more vital to the offense.

Contain Ezekiel Elliott

Last year, the Redskins beat visiting Dallas, 20-17, by holding Ezekiel Elliott to 33 rushing yards in one of the worst games of his career. When they played again a few weeks later, Elliott ran for 121 yards in the Cowboys’ 31-23 home win. Some of that production was the result of the recently acquired Amari Cooper’s eight catches for 180 yards, but the pattern is clear: Contain Elliott and you take away what Dallas likes to do best.

Elliott was sluggish last weekend, running for 53 yards after coming back from his summerlong holdout. But the Cowboys’ line is so good and Prescott was incredibly accurate in finding Cooper and second-year wide receiver Michael Gallup that it won’t take much for Elliott to be Elliott again.

Cut out offensive line penalties

The Eagles trampled the Redskins in the second half, but Washington’s offense did its defense no favors by going three and out on its first three possessions after halftime. Each of those drives was compromised by a penalty by an offensive lineman. Similar problems hampered the offense last year, especially in the season’s second half, when injuries left Washington piecing together its line.

The Redskins have had to throw together another line amid the holdout of star left tackle Trent Williams, signing tackle Ereck Flowers and moving him to left guard and bringing in Donald Penn to play tackle. It hasn’t been the disaster many have feared. The linemen have talked a lot about “cleaning up” the mistakes from last week, but those will have to be fixed fast.

Stop DeMarcus Lawrence

Even when Cowboys defensive end DeMarcus Lawrence isn’t sacking the quarterback, he is dangerous — and disruptive. Last week, he was everywhere in the Giants’ backfield, forcing bad throws and cutting off the running game. Washington quarterback Case Keenum did a good job of avoiding the pass rush last week, but he might have to be even better Sunday if the line can’t stop Lawrence.

More on the Redskins:

Derrius Guice to injured reserve; Jonathan Allen and Jordan Reed out for Redskins-Cowboys game

Analysis: The Redskins say they have a great defensive line. The numbers don’t show it.

Inside the four drives that doomed the Redskins in their loss to the Eagles

Santana Moss says the Redskins deactivating Adrian Peterson was ‘ludicrous’