A look at the New York Giants Week 12 performance against the Dallas Cowboys. Fading fast? The New York Giants 28-20 loss to the Dallas Cowboys on Thanksgiving means Big Blue is now 1-4 in its last four games, including before the bye. Moreover, most of the formula the Giants relied on to win games in the first half of the season seems to have lost its potency. Teams have figured out how to stop running back Saquon Barkley. The defense’s third-down and goal-line proficiency has also eroded. And it’s as if all of a sudden, the Giants, once the…