Last night’s “Sunday Night Football” preseason game, in which the San Diego Chargers defeated the Dallas Cowboys, 20-7, delivered a 7.1 overnight rating and 12 share (8:15-11 p.m. ET), the best overnight rating for any NFL preseason game on any network this year. The game peaked at an 8.1/13 from 9-9:30 p.m. ET.