The owners must be seeing catastrophically bad season ticket renewal numbers.
A number of teams are down in renewal numbers. Also, teams are dropping ticket prices or (at best) keeping them the same as last year.
https://www.usatoday.com/story/sports/nfl/2018/01/16/jets-reducing-ticket-prices-on-average-11-percent-for-2018/109509276/
Here’s just one example