NBC, known for “Sunday Night Football,” will now have one major sport or another on Sunday evenings across the whole year. “Mike is a unicorn,” says Rob Hyland, the executive producer of NBC’s “Sunday Night Football.” He’s talking about Tirico’s superhuman ability to toggle between important assignments. Kirk Herbstreit, who enjoys prominent roles with both ESPN and Amazon’s “Thursday Night Football” coverage, has a particularly gnarly schedule. Without three hours of “Sunday Night Football,” “the highlights don’t exist,” says Drew Esocoff, the veteran sports director who helps guide “Sunday Night Football” behind the scenes. “I’ve never called a baseball game,” Tirico says.