The Cowboys defense had played flawlessly for nearly the entire first half on Sunday, limiting Kansas City to just a field goal.
With only a few seconds before intermission and the Chiefs 56 yards from the endzone, Dallas committed one of the biggest blunders the NFL has seen this season. The Cowboys dropped seven defenders to the goal line, allowing Kansas City to dump it underneath to their speedster Tyreek Hill.
And on a perfectly designed play, the Chiefs scored one of the most bizarre touchdowns of the year to end the half. Even Tony Romo was stunned in the broadcast booth.
For many – myself included – it felt as though momentum completely shifted to Kansas City. Surely that would wake up the high-powered Chief offense, wouldn't it?
Instead of feeling sorry for themselves, Dallas' defense came up big in the second half –and were one of the main reasons the Cowboys won this game. Dallas surrendered just one touchdown in the final 30 minutes, ended Alex Smith's streak of passes without an interception, and held Kansas City to 4-of-11 on third down conversions.
The defensive line, led by DeMarcus Lawrence and David Irving, dominated the line of scrimmage and bottled up Kareem Hunt. Kansas City managed just 68 yards rushing on 19 attempts, resorting to their passing game for most of the afternoon. In return, Dallas' young secondary responded, giving up only 255 yards to Smith through the air.
The Cowboys entered the game 15th in the NFL in both passing and rushing defense, but Rod Marinelli's unit played much better than that against one of the best offenses in the NFL.
Dallas sacked Smith twice and were constantly flushing him out of the pocket. Sean Lee, Jaylon Smith and the secondary were flying to the ball. And aside from the big play to Hill to end the first half, the Cowboys' secondary never got burned.
After Dallas went up by 11 with 8:58 remaining in the fourth, the defense slammed the door on Kansas City completely, thwarting any attempt at a comeback. It was a nice change of pace for a team typically reliant on its offense to seal the deal.
With Ezekiel Elliott's future still uncertain and Dez Bryant, Terrance Williams and Tyron Smith sustaining injuries, Dallas will need its defense now more than ever. Usually it's the offense that's picking up the slack, but their performance against Kansas City showed just how good the Cowboys' defense can be.
With Atlanta and Philadelphia up next, things won't get any easier for Dallas defensively.
But if they play like they did Sunday, the Falcons and Eagles had better take notice.
You can thank Reece on Twitter @ReeceWaddell15 for showing the restraint by not mentioning Jeff Heath even once.