Instead, an outfit called Strikeforce has underwritten the match as part of its effort to gain some purchase in the thriving mixed martial arts business. With varying degrees of success, other upstart ventures have sought to distinguish themselves as the team league and the Hispanic league. Strikeforce has cast its lot with women.

“I think they’re capable of delivering the excitement and the competitiveness,” said Mike Afromowitz, a spokesman for Strikeforce. “That’s what we need and the fight needs in order to have women headlining in future bouts.”

Some women in more traditional sports have embraced the publicity.

“Any exposure of women combatants is probably good exposure in general,” said Christy Halbert, a coach of the national women’s boxing team, who has campaigned to have her boxers accepted alongside men in the 2012 Olympic Games. “There’s a lot of women boxers out there who deserve to make a living in their chosen profession.”

The general manager for sports programming at Showtime, Ken Hershman, said Carano would face “a lot of pressure, but that’s the way it should be, right, if you’re going to headline?”

For Carano, the middle daughter of a backup quarterback for the Dallas Cowboys, the release valve has taken the form of a rich inner life. She travels to Chicago just to drive around neighborhoods where the houses look different. She walks the dogs. She counsels her roommate, an old friend who served time in prison for drunken driving and other nonviolent offenses, to improve himself with computer classes. She studies Beethoven sonatas. And she talks up mixed martial arts with a confident humility.

“When I first started,” she said, “in Showtime I was called the pet project: ‘Here, I’m going to help you out and put you on this show.’ In my head, I’m like, I train and work out like everyone else. They like to tell you what you’re not. They like to keep you down, so they can get more out of you for their money. But fans don’t lie. When they’re all chanting your name, you know they’re supporting you. So we went from being the pet project to now we’re headlining an event. So this is huge for me.”