Jeff Fisher's now the honcho of an indoor football league, and he tells TMZ Sports he's looking to grow it drastically in the next year ... perhaps with the help of a few high-profile celebs.
The former NFL head coach was recently named commissioner of Arena Football One ... and while the org.'s enjoying a successful inaugural season this year -- he said 2026 "is going to be an eye-opener for everybody."
Currently, the league has just eight teams -- but Fisher said there could be as many as 16 by next season.