“RedZone,” the channel that shows key plays in real time, will continue to be produced by the NFL, with Scott Hanson as host. ESPN will have linear TV rights to the channel — as well as the right to the brand to expand it to other sports — but the NFL still controls digital distribution.

But the declining interest in boxing as a sport is a reminder that a sport’s popularity can wane if the people in charge make it increasingly expensive for fans to follow it. Some will find it hard to even imagine that America’s most popular and profitable sport could soon face an existential crisis.