It's just a matter of time before the NFL expands from 17 regular-season games to 18. (And then 19. And then 20.)

The possibility of one more game has prompted plenty of talk about adding a second bye. During a London fan forum on Saturday, Commissioner Roger Goodell addressed the issue of giving all teams a second week off.

"A lot of that depends on -- can we continue to make the game safer, can we continue to modify the way we conduct the offseason as well as the training camp and as well as the season, so that these guys feel comfortable being able to play that period of time?" Goodell said, via ESPN.com.

Those factors, if achieved, would point to sticking with one bye. Which would be the only way to make a full season fit between the Thursday after Labor Day and President's Day weekend. Adding a second bye would force the NFL to start on Labor Day weekend. The league last played on Labor Day weekend in 2001, because viewership is lower during the last unofficial weekend of summer.

Also, the NFL used two byes in 1993. The networks didn't like it; the weekly schedule became diluted.

Much of it comes down to whether and to what extent the NFL Players Association pushes for a second bye. The union, as we've said before, needs to put up more of a fight against 18 games, in order to get more concessions from the league.

Even if the owners can essentially force an extra game at the conclusion with the threat of a lockout as of March 2031, when the current labor deal expires, the only way to add an 18th game before then is to get the NFLPA to agree to it.

Which gives the union leverage that it should use to the fullest. Including a second bye.