As the football season gets ready to kick off, a few new schedule wrinkles for America’s most popular sport could affect the primetime network ratings race.

NBC, whose primetime “Sunday Night Football” overtook a declining “American Idol” to stand as TV’s most-watched series for the 2011-12 season, will see its package expand once again.

“SNF” aired 17 regular-season games during NBC’s first year back with the NFL in 2006, and that number grew to 18 a couple of years ago (adding a game opposite the World Series, after traditionally yielding to baseball on the night). And now, NBC’s sked will grow to 19 games as the net takes over the primetime Thanksgiving contest (this year it’s the Patriots against the Jets) that had aired on NFL Network.

Only 17 of the league’s 32 teams are scheduled to appear on NBC, with three appearances apiece by the Cowboys, Giants, Packers, Patriots and Steelers. It will be hard to match last season’s “SNF” average aud of 20.7 million (the mega-draw Cowboys appeared four times, twice against the Giants), but an extra game will certainly help boost NBC’s fourth-quarter averages.

At ESPN, “Monday Night Football” should bounce back after a drop in ratings last season due to lackluster matchups too often featuring teams with little marquee appeal (hello, Jacksonville Jaguars). Looking to appease the network that shells out more money annually than any football network, the NFL has beefed up the “MNF” sked for what could be its highest-rated season yet.

While 23 teams will appear on “MNF” this coming season, that is actually a few less than last year, meaning no appearances by the teams deemed to be among the weakest — including the Browns, Buccaneers and Vikings. There are also more teams from top-10 markets featured on ESPN, including a pair of games each for the New York Jets, Houston Texans and San Francisco 49ers and three appearances by the Chicago Bears.

A stronger “MNF” could hurt male-appeal Monday shows like “Hawaii Five-0” and NBC’s new “Revolution.”

Also something to contend with for competing networks this fall, but to a lesser extent, is NFL Network’s “Thursday Night Football,” which will now start in September instead of November. The quality of this package is not nearly as good as “SNF” or “MNF,” though, and it is here viewers will see some of the lightweight teams.

Another change this year is the league’s shift of late-afternoon doubleheader games on CBS and Fox from 4:15 p.m. ET to 4:25. This was primarily done because the league’s new overtime rules could make for longer games, but also to allow viewers in more markets to watch the conclusion of their 1 p.m. ET contests before switching to the top-drawer matchup that caps the afternoon.

This will mean bottom-line gains for CBS and Fox as action on their respective doubleheader weeks should run about 10 minutes deeper into primetime. It also could hurt NBC slightly, as its pregame coverage for “SNF” will be competing more often with live action.

Fox airs a postgame show up until 8 p.m. so “The Simpsons” can start on time, but old-school CBS still starts its taped “60 Minutes” late, frustrating fans of the three shows that follow it.

On the college side, ABC will again air games most Saturdays, but will be joined by Fox, following the dissolution of the net’s longtime combo of “Cops” and “America’s Most Wanted.”

The Fox games from the Pac-12 conference will start at around 7:35 p.m. ET, so it won’t be a direct overlap with ABC’s games (8:15 ET), which will be mostly Big Ten and Big 12 action, but they will certainly cannibalize some of each other’s viewership.

Still, when it comes to football, there are usually enough fans to go around.