To do it, Mike Shanahan's team must attack an injury-riddled group of linebackers and get in the face of quarterback Tony Romo.
Offense: Crossing Patterns, Crossing Patterns and more Crossing Patterns
Kirk Cousins and his receivers must attack the area behind the Cowboys linebackers and in front of the safeties. That means a heavy dose of crossing patterns designed to get behind the second level.
The Dallas defense has had major issues dealing with these routes. Last week, the Green Bay Packers produced a big gain off a crossing pattern on their first possession.
The Packers ran both wide receivers, James Jones and Jordy Nelson, behind the linebackers and in front of the safeties.
Quarterback Matt Flynn hit Jones in the void between the second and third levels of the defense.
Jones then outran his pursuers and completed a 39-yard pass play.
The Washington offense can use this same play design to expose the Cowboys' weaknesses in coverage. Against the Atlanta Falcons in Week 15, the Redskins used a crossing pattern to free Pierre Garcon for a big play.
Garcon simply ran a short slant behind the linebackers.
Cousins hit him in stride in front of the deep safety. Garcon took the pass on the run and scampered to finish a 27-yard gain.
One of the main reasons the Dallas defense has failed this season is because it doesn't boast linebackers and safeties competent enough for coordinator Monte Kiffin's zone schemes.
If running back Alfred Morris produces another big game against the Cowboys and their 28th-ranked run defense, it will be put even more stress on the linebackers and safeties.
Given his prolific history against the Cowboys, Morris can set up numerous play-action opportunities that will create huge gaps between the second and third levels of the defense.
By flooding the voids in these zones, the Redskins can fashion a number of significant gains. They can also turn a pair of forgotten playmakers loose.
Get Fred Davis and Roy Helu Jr. Involved
Offensive coordinator Kyle Shanahan has to make more use of all the weapons at his disposal. Against the Cowboys, that should mean getting tight end Fred Davis and running back Roy Helu Jr. more involved.
Davis reminded everyone he still wears burgundy and gold by catching a touchdown in Atlanta last week. He was filling in for rookie Jordan Reed, who continues to struggle to shake off the effects of a concussion.
He is set to visit with another concussion specialist, according to The Washington Times' Brian McNally, so Davis could be called into action again. If used more often and in more creative ways, he can be a matchup nightmare for the Cowboys.
The Dallas defense has found it hard to corral tight ends in recent weeks. In Week 15, Packers starter Andrew Quarless burned them for six catches for 66 yards and a touchdown.
Not surprisingly, he was particularly dangerous on crossing routes. On this play, the Packers would run three slants, with Quarless coming off the slot on the left side.
This was the perfect answer to a Cowboys blitz scheme and challenged their single-high coverage. The deep safety was put in a bind over which slant route to cover.
Flynn wisely targeted the 6'4", 252-pound Quarless, who again got behind second-level coverage and in front of the safety. The play was good for 14 yards.
Davis, at 6'4" and 247 pounds, can also thrive on these routes. But that shouldn't be the limit to how the Redskins use him.
Shanahan must take advantage of his move skills, the way he did with Reed against the Cowboys in Week 6.
In this example, Reed began in a flex alignment, similar to an H-Back role. He would release out of the backfield and run a circle route to get behind the second level of the Cowboys' nickel front.
Quarterback Robert Griffin III wasted no time targeting Reed against single coverage. The first-year talent beat safety Barry Church and produced a 29-yard gain.
Davis can be used the same way, just as he was against the Cowboys in Week 11 of the 2011 season. On this play, Davis was flexed in the slot, but would release behind the line and across the formation.
Once he got behind outside linebacker Anthony Spencer, Davis was wide open to receive Rex Grossman's pass and complete a 24-yard catch and run.
Davis may be out of favor as a pending free agent, but that shouldn't mean the Redskins waste his hybrid skills in a game where they can do real damage.
They also shouldn't waste Helu, although that message clearly hasn't made it to the coaches this season. Where 2011's fourth-round pick can be really effective is on screen plays, releasing behind pass-rushing defensive ends.
Both DeMarcus Ware and George Selvie have one mission on the Cowboys defense and that is getting to the quarterback. They will always rush upfield and can be caught out of position.
A great way to do it is to run screens behind their rush. The Packers did that to produce a critical score last week.
They ran Quarless and fullback John Kuhn off the line to help clear the way for running back James Starks.
To sell the rouse, the Packers let Ware through clean. Starks initially blocked him to slow down his rush before releasing behind Ware.
Flynn simply dumped the ball over Ware to Starks, who already had a convoy of blockers in front.
Running behind his blocks, Starks powered his way into the end zone.
This was a beautifully designed play that took advantage of the overaggressive tendencies of the Dallas defense. It was simplicity itself and can work wonders for a speedster like Helu.
He is a genuine big-play threat any time he gets the ball in space. A few significant gains off screens like this will slow down a Cowboys pass rush that gave the Redskins fits in Week 6.
As for the Washington defense, it can cause a few headaches with some carefully directed pressure.
Pressure the Inside
The Cowboys are strong at the edges of their offensive line. Tackles Doug Free and especially Tyron Smith are tough to get around.
But where they are vulnerable is on the inside. The Redskins can attack this weakness with middle pressure.
Defensive coordinator Jim Haslett should take a page from the Packers and design some blitzes to free his best pass-rusher through the middle.
Take a look at what the Packers did late in the third quarter. They positioned top rush end Clay Matthews (52) in the middle next to inside 'backer A.J. Hawk.
The pair would run a stunt with Hawk going first and Matthews looping around him. That twist challenged the center and left guard.
As Hawk drew both their blocks, Matthews had a free run at Romo. His pressure forced the quarterback to flee the pocket where he was felled by rookie Datone Jones.
Haslett can draw up similar blitzes to position stud pass-rusher Brian Orakpo on the inside. It is something the Redskins should do more often anyway and can cause the Cowboys a host of problems.
The Washington defense must keep the pressure in the face of Romo. That is the quickest way to force him into some rash decisions and inevitable mistakes.
Another sure way to frustrate Romo will be to commit to taking away his favorite receiver.
Shut Down Jason Witten
Romo is still at his best when he is allowed to establish a rapport with his tight end. The Redskins kept Witten quiet in Week 6 and must do the same again this Sunday.
That means making a commitment to doubling the crafty veteran. Playing in perhaps his final home game, London Fletcher may want the job of shackling Witten underneath.
But despite Fletcher's expertise, Perry Riley Jr. could be a better fit for the task. He is a superior size matchup against Witten and has improved considerably in coverage this season.
Riley should be supported either by an outside linebacker, or a safety, depending on Witten's route. By taking away Romo's safety valve, the Redskins will force him to beat them with somebody else.
That will be a tough task with pressure swarming around him. A focus on Witten will demand a strong game from cornerback DeAngelo Hall against talented but inconsistent wide receiver Dez Bryant.
Hall can handle the job, having kept Bryant to just 36 yards in Week 6. That will leave underneath defenders to gang up on Witten.
Even at 3-11, the Redskins should have all the motivation they need to derail the suddenly slumping Cowboys. If Cousins attacks the right areas and the defense stays after Romo, expect Washington to upset the old enemy.
All screen shots courtesy of Fox Sports, NBC Sports and NFL.com Game Pass.