The NFL adopted flexible scheduling with it's primetime games in 2006, and today, they tok another step in ensuring that the biggest games of the week involve more quality opponents.
According to NFL.com's Gregg Rosenthal, the NFL can now start flexing games as early as Week 5:
Around The League has learned that games can be flexed into Sunday Night Football as early as Week 5, according to a league source. In the past, "flex scheduling" did not start until Week 11.
The potential flex games between Week 5 and Week 10 come with a stipulation. The NFL can't change the tentative Sunday Night Football game every week. The league can flex up to two games total into Sunday night between Weeks 5-10. The rest of the flexible schedule procedures from previous years remains intact. After Week 11, the NFL can flex any Sunday night game.
As before, only Sunday afternoon games are subject to being moved into the Sunday night window. Thursday, Saturday, and Monday games are not affected. Flex scheduling allows the league to handpick a game to be moved into the Sunday Night NBC window, avoiding lackluster matchups.
The NFL opts to flex games after negotiating with networks, and not all games are flexible. Last year, CBS protected the rights to the Cincinnati Bengals' game against the Indianapolis Colts, or else, that could have been a game that was flexed into the Sunday night primetime slot.
The announcement will come no later than 12 days prior to the Sunday night game for Weeks 5-16.