Running back Saquon Barkley dodged and bulled his way to a 5-yard gain on the first play from scrimmage in Sunday’s game between the Giants and Denver Broncos. Barkley, the cynosure of the Giants’ offense until a torn knee ligament kept him out of 14 games last season, seemed whole again, and the home fans at a packed MetLife Stadium leapt to their feet in response.