The Super Bowl wasn't the only headliner on Sunday night. After overtime and ample post-game coverage, Fox used the prime (technically late-night) window to launch 24: Legacy.

In its first outing, the spinoff of the network's original counterterrorism drama averaged 17.6 million viewers and a 6.1 rating among adults 18-49. As total reach goes, the hour was down about 3 million viewers (14 percent) from last year's post-Super Bowl offering on CBS — a special episode of Stephen Colbert's Late Show.

Fox's 24: Legacy had an advantageous lead-in. The linear telecast of the New England Patriots' overtime victory over the Atlanta Falcons — that is to say, the Fox broadcast without any streaming boost — averaged 111.3 million viewers. But the late finish time seemed to take some wind out of 24: Legacy's sails. The show may now rank as the best broadcast network series launch since CBS' 2 Broke Girls in 2011, but it also ranks among the least-watched Super Bowl lead-out programs in recent history. (With a 11 p.m. ET start, it was the third-latest on record.)

It is at least a bigger showing than that of Alias. The 2003 post-Super Bowl show, back when ABC was still in the game's rotation, started at a very late 11:15 p.m. and averaged 17.4 million viewers.

Launching a new show out of the Super Bowl was a bold move. Networks typically use the spot to bolster flagships, but it is not without precedent. The last series to debut out of the Super Bowl was Undercover Boss in 2010. CBS saw the reality show debut with an astronomical 38.7 million viewers, still the best showing since 2001.

The real measure for 24: Legacy will be how many people tune into that premiere on other platforms — as well as Monday's subsequent time slot premiere.