The Cowboys had a real chance to win in Foxboro and end Tom Brady's home winning streak, but Jason Garrett took the role that Tony Romo had played two weeks ago and shot his team in the foot. Let's get this out of the way first: once you're unable to score a touchdown from 2nd-goal at the five, you're probably going to lose that game. Garrett's play call on 3rd-goal was conservative and relied on fooling the interior of the New England defense. It didn't work. Fine.
His defense offered him one last unexpected lifeline, though, and instead of taking that bull by the horns, Garrett backed off and said 'I'll take my defense against Tom Brady in Foxboro on one final drive to win the game.' I don't care how much Garrett believes in his defense, you can't make that decision.
Garrett's approach Sunday - running right into the Patriots front, which had stuffed him all day and was clearly geared up to stop the run on that drive - was clearly in response to Romo's struggles with leads in New York and against Detroit, but he changed approaches at the worst time imaginable. Going conservative with a lead against Mark Sanchez makes a lot of sense. Going conservative with a big lead against a Lions offense that had no momentum makes some sense. Doing what he did today makes zero sense.
You're 1st-10 at your 28 with 3:36 remaining with a three-point lead and the Patriots have all of their timeouts remaining. Throwing the ball behind your iffy offensive line means that bad things could happen. Romo could throw an interception, and, more likely, if you call a play with a real chance at picking up a first down, you have a good chance of an incompletion and a stopped clock.
The alternative, though, is giving Brady just enough time to beat you - and he's almost always going to do that, even against defenses better than yours. Stopping the clock actually isn't that bad of a thing in that instance because the reality is that you want some time on the clock anyway, if your passes are incomplete and the Patriots do score.
Garrett was looking at a hand stacked against him whichever way he went, but any real chance of winning that game rested on finding a way to keep the ball away from Tom Brady. He didn't even try to do that, and he died the slow death he deserved to as a result.