Patriot Place & Gillette Stadium
A few restaurants are open -- Davio's, Red Robin Burgers and ???, but most of Patriot Place seems to be under construction still, and several places are only opened during the evening. I don't know what their plans are for game days.
Near the stadium, selection is pretty slim. I suggest the Chieftan in Plainville, but they're closed on Sundays. Layfette House is nearby for a burger and beer + parking. And north of the stadium is a new place called Wicked, which has a large outdoor deck. I haven't been yet, but the buzz has been pretty decent. Just north of that in Walpole (across from the Walpole Mall) is British Beer Company. Plenty of beers on tap, but the food is pretty meh. Tailgating will very likely get you better eats if you plan it right.