The Dallas Cowboys can clinch the NFC East crown with a Week 18 victory over the Washington Commanders, but one fatal flaw might prevent the Lombardi Trophy from making a return to Texas for a 28th consecutive season.

Even as the Cowboys are poised to finish as high as the No. 2 seed in the NFC, Dallas has struggled to get its rushing defense back on track ever since being gashed for 266 yards by the Buffalo Bills back in Week 15.

ESPN’s Bill Barnwell identified the fatal flaw of some of the top Super Bowl contenders as the playoffs loom and before the regular season finale, listing the Cowboys’ run defense as a major concern.

“If you get an early lead, though, you’ve got a shot [against Dallas],” Barnwell wrote on January 4. “The Cowboys aren’t as effective when they’re forced into a dropback passing attack. More noticeably, though, the Cowboys struggle to stop the run. They’re 31st in defensive success rate against the run, meaning opposing offenses stay ahead of schedule or pick up first downs or touchdowns on the ground at the NFL’s second-highest rate. A team that doesn’t have Leighton Vander Esch right now and uses 205-pound converted safety Markquese Bell as a starting safety most weeks doesn’t want to be in a position to chase down ball carriers over and over again as the game goes along.

“We’ve seen this pop up repeatedly in Cowboys losses. In Week 3, the Cardinals ran the ball 30 times for 222 yards and two scores, the 12th-most rushing yards by any team in a single game all season. The 49ers dropped 41 carries for 170 yards in their blowout win a couple of weeks later, albeit in a game where the Cowboys held Christian McCaffrey to 51 yards on 19 rush attempts. The Bills really sealed the image of the Cowboys, though, by racking up 266 rushing yards on 49 carries in their comfortable victory over Dallas in December, including a 25-carry, 179-yard performance from James Cook.”

As those dominant performances by top backs mentioned by Barnwell illustrates, the Cowboys have struggled to overcome a team jumping out to a lead and being able to salt out a win by running the football.

Dallas enters Week 18 as the No. 20-ranked rushing defense in the NFL, allowing 116.25 yards per game, the worst among teams that have clinched a postseason berth in the NFC.

Cowboys’ Nightmare Playoff Opponent Looms
Almost since the moment the final whistle was blown in the San Francisco 49ers‘ 42-10 blowout victory over the Cowboys in Week 5, a war of words ignited that has intensified throughout the course of the season.

One bright spot for the Cowboys was their defense holding Christian McCaffrey to just 51 rushing yards with a touchdown.

Despite their strong showing against one of the NFL’s MVP front-runners, the 49ers would be a nightmare for the Cowboys should the two teams meet in the NFC Championship, Barnwell wrote.

“Well, you’ve seen the two recent playoff games and the blowout loss earlier this season, right?” Barnwell writes. “The Niners convert 29.4% of their rush attempts into first downs, the NFL’s second-best rate, and 46% of their runs result in successful plays for the offense by EPA, which is fourth-best. McCaffrey’s calf injury could complicate things, but Jordan Mason had 10 carries for a season-high 69 yards when these two teams played earlier this season.”

McCaffrey would likely have revenge on his mind, if he’s fully healthy, but in order to get past San Francisco and into the franchise’s first Super Bowl in a generation, the Cowboys would need to get by the NFL’s No. 3-ranked rushing offense.

Dalvin Cook Signing Looming to Boost Cowboys’ Rushing Offense?
The Cowboys could be in the mix for Dalvin Cook after the New York Jets waived the veteran running back on January 3.

When asked about Dallas potentially adding Cook for the upcoming playoff run, Cowboys head coach Mike McCarthy didn’t dismiss the idea.

“Those are questions you are always visiting with and so forth,” McCarthy told reporters. “Obviously I have a tremendous amount of respect for him, played a number of games against [him] when Dalvin was in Minnesota. I have great respect for him.”

Cook struggled to see the field in a limited role with the Jets, rushing for only 214 yards on 3.2 yards per carry.

But, the Cowboys could make some sense as a landing spot for Cook, especially with rookie Deuce Vaughn heading to injured reserve and a lack of quality depth behind Tony Pollard.

After clearing waivers, Cook is an unrestricted free agent and free to sign with the team of his choosing.