Enter areas like the Jaguars’ lounge, which is open to any fan in the stadium for no extra charge and offers air-conditioning, fast WiFi connections, video-game stations, comfortable recliners and food and drinks. The field of play is partly visible from the lounge, but that is almost incidental, and last Sunday, the Jaguars’ game was merely one of several on the TVs.

The Jaguars realize that in the fight for fans’ attention and wallets, their competition is not just from college football and other sports, but from fantasy football, social media and the highlights, statistics and online discussion that can sometimes be hard to follow in stadiums but have become an essential part of N.F.L. Sundays.

“The most important thing is to make sure they have a good game-day experience,” said Khan, who, during the game, stopped by the lounge, above the end zone on the stadium’s south side. “Teams like us are looking for every competitive advantage.”

In effect, teams are trying to marry live football with the digital experience. In fantasy football, fans create “teams” with real players and compete to see whose players perform the best statistically in any given week.

“Fans are left in the dark when they go to the stadium because the home experience has improved so dramatically,” said Phil de Picciotto, the president of Octagon, a sports marketing agency. The fantasy lounge in Jacksonville, he said, is “in part life imitating art imitating life and in part, if you can’t beat them, join them.”

It is a far cry from the years when about the only way to see your favorite team was to buy a ticket and the only way to get details of other games while sitting in the stands was to have a transistor radio handy.

Smartphones have helped blend the home and stadium experiences, allowing fans to check their fantasy scores while at games. Yet overloaded networks have made for spotty connections, and the technological advantages of staying home gave fans a reason to do just that. It is one reason that after peaking in 2007, leaguewide attendance has slowly declined. The challenge is especially great for struggling teams like Jacksonville, which finished 2-14 last season.