PHILADELPHIA — The team clad in midnight green uniforms and white pants also wore winged helmets. Its game Saturday night was — checks notes — contested in Philadelphia. So it stood to reason that the team had to have been the Eagles, though not even the most loyal of the team’s tailgating fans might have recognized the surnames on the backs of many of those jerseys.

Welcome to the final week of the N.F.L.’s expanded regular season, where the league’s desire for Still More Football produced a game on Saturday between two playoff-bound teams who had little incentive to play their starters.

So the Eagles didn’t. The Cowboys did, and Dallas’s decision to dress stars like Dak Prescott and Ezekiel Elliott and Amari Cooper affirmed that they were capable of walloping Philadelphia’s reserves.

If nothing else, the Cowboys’ 51-26 victory enabled them to feel a smidgen better about the postseason. Afterward, Coach Mike McCarthy said it had been imperative that his team rediscovered the offensive consistency that — with one grand exception — had been lacking the last five weeks. The brief faltering prompted the team’s owner, Jerry Jones, to say in a December radio interview that it was “probably fair” to categorize Prescott as being in a slump.

In the first half alone, the Cowboys averaged 9.3 yards per play and Prescott threw four of his five touchdown passes. In setting the franchise’s single-season record at 37, Prescott affirmed that the Eagles (9-8) would be wise not to send out their seventh-string secondary in the N.F.C. wild-card round next week.

“I think it’s a hell of a year,” McCarthy said, deadpan, “for a guy who was in a slump.”

Told of those comments, Prescott said, “If I wasn’t in one, I guess I would have done it a while back.”

Though the Cowboys (12-5) had chances against Kansas City, the Raiders and Cardinals, until Saturday they hadn’t beaten a team with a winning record since Week 4, when they beat the Panthers, who are now 5-11. Those flops coincided with a stretch, loaded with dropped passes and penalties, turnovers and Prescott’s own poor decision-making, that sapped Dallas’s offensive potency. It returned, briefly, in a Week 16 romp of Washington, then vanished again, in a loss last week to the Cardinals.

That is why, despite their own raft of unavailable players, the Cowboys prioritized gaining confidence — and a victory — over risking injuries in an otherwise meaningless game.

“I’ve rested players, I’ve not rested players,” said McCarthy, who previously coached the Green Bay Packers for 13 seasons. “But we felt where we were as a team, our first year in the playoffs, it was important for us to play.”

It was important for Prescott, who looked comfortable dissecting the Eagles’ defense, completing 21 of 27 passes for 295 yards. It was important for receiver Cedrick Wilson, who, with Michael Gallup out for the season with a torn knee ligament, continued his emergence as a dependable third receiving option, catching five passes for 119 yards and two touchdowns. And it was important for running back Ezekiel Elliott, hampered with a knee injury much of the season, who gained 87 of Dallas’s 171 rushing yards then proclaimed himself healthy for the postseason.

The Cowboys scored on eight of nine possessions, excluding kneel-downs, and for a rivalry so steeped in antipathy, with tales of Bounty Bowls and pickle juice and flying pork chops, this installment featured all the excitement of a beige sofa.

As Dallas traveled without linebacker Micah Parsons, left tackle Tyron Smith and running back Tony Pollard, among others, Eagles Coach Nick Sirianni opted to rest 16 starters — not including center Jason Kelce, who played only the first snap, just to extend his consecutive-start streak to 122 — and elevated 12 players from the practice squad.

Under Sirianni, Philadelphia’s first-year head coach, the Eagles more than doubled their victory total from last season’s 4-11-1 fiasco, throttling bad teams and backup quarterbacks with a run-heavy offense led by quarterback Jalen Hurts to win six of their final eight games. Still recovering from a high ankle sprain, Hurts sat Saturday in place of Gardner Minshew, but Sirianni said he will be ready for the Eagles’ playoff game.

The only way Philadelphia can rise to sixth from seventh in the N.F.C. is if New Orleans defeats Atlanta and the Rams beat San Francisco. The Cowboys, as N.F.C. East champions, won’t fall below fourth but could move as high as second.

Either way, they will host a playoff game, and though everyone from Prescott to McCarthy to DeMarcus Lawrence emphasized their second-by-second focus heading into next weekend, it did not require much imagination to recognize that the Cowboys, with a first-round victory, could wind up facing the top-seeded Packers, in frigid Green Bay, Wis.

Capping a season in which they swept all six games from divisional opponents and finished with the most points in a season in franchise history (530), the Cowboys’ dominance on a chilly night Saturday warmed their spirits before heading home.

“When the plane touches down in Dallas,” McCarthy said. “That’s the starting line.”