National Football League teams are facing a significant threat to their finances because of a legal option available to nearly every janitor, teacher and cashier in America — workers’ compensation. Playing professional football is inherently dangerous, but the known risks do not prevent players — and former players — from filing workers’ compensation claims against teams, courts have ruled. And while an individual compensation award might cost a team just $20,000, the changing types of claims being filed could end up costing teams millions of dollars a year.