Fox’s “American Idol” returned to wreak havoc on the competition last week, but TV’s hottest comedies — ABC’s “Modern Family” and CBS’ “The Big Bang Theory” — emerged unscathed from their first head-to-head battles.

As it kicks off its 11th season, “Idol” looked a bit more mortal. Nielsen estimates that Wednesday’s two-hour opener averaged a 7.4 rating/19 share in adults 18-49 and 21.93 million viewers overall (down 23% in the demo from last year) and Thursday’s premiere hour (5.7/15, 18.02m) was off 27%.

Even with its weakest start since its initial run in summer 2002, “American Idol” accounted for the week’s three top programs among young adults (including Sunday’s post-football special).

Biggest news during “Idol” premiere week, though, was the strong tune-in for both “Modern” and “Bang.” Though each is among the biggest gainers in DVR playback (the ABC show is No. 1), auds showed up on their premiere nights last week even with the tougher competish from Fox.

“Big Bang” (5.3/15 in 18-49, 15.83m) became the first regular in-season series to top “Idol” head-to-head in 18-49 (5.3 to 5.2), up 26% vs. a year ago when “Idol” crushed it (7.0 to 4.2). And “Modern Family” (5.1/12, 11.89m) grew year-to-year by 11%. Both shows impressively matched their week-earlier scores.

Still, Fox dominated last week like no net has this season thanks to the combo of “Idol,” a good start for Monday drama “Alcatraz” (3.3/8, 10.05m) and a monster Sunday football game (21.4/47, 57.63m for Giants-49ers). Its 7.7/19 in 18-49 was more than the other five broadcast networks combined: 2.1/5 for both ABC and CBS, 1.5/4 for NBC, 1.4/4 for Univision and 0.5/1 for CW.

The huge frame helped Fox leap-frog CBS for the season lead in 18-49, which should hold up even with a softer “Idol.”

At CBS, Thursday stayed strong post-“Big Bang” with week two of “Rob” (3.5/9, 11.41m) and the above-average “Person of Interest” (3.2/8, 14.40m) and “The Mentalist” (3.0/8, 14.22m). Also hot were Wednesday’s “Criminal Minds” (3.2/8, 13.00m, up vs. last year against “Idol”) and “CSI” (2.8/7, 12.02m).

At ABC, “Modern Family” lead-out “Happy Endings” (2.9/7, 6.06m) was up 21% vs. “Cougar Town” a year ago. Also, Tuesday laffer “Last Man Standing” was up (2.6/7, 8.59m) and Sunday’s “Once Upon a Time” (3.2/7, 9.33m) was solid vs. football.

NBC surged Monday with “Betty White’s 90th Birthday” special (2.7/7, 13.86m), and rookie drama “Grimm” shined on Friday (1.8/5, 5.92m). Not so hot is “The Firm” (3.42m), whose second Thursday seg ran eighth in 18-49 at 10 o’clock.”Drew Peterson: Untouchable,” starring Rob Lowe, was TV’s No. 1 primetime show Saturday (1.7/5, 5.77m) and the most-watched cable telepic in two years.

TNT scored big with Thursday’s Heat-Lakers NBA game (2.0/6, 4.40m); FX’s “Archer” was solid kicking off its third season (1.31m) even opposite hoops action; Science’s season preem of “An Idiot Abroad 2: The Bucket List,” featuring Ricky Gervais, was the net’s top telecast ever in 18-49 (480,000) and 25-54 (538,000); Bravo’s “Real Housewives of Beverly Hills” hit season highs Monday (1.3/3, 2.76m); and Nickelodeon’s “iCarly” on Saturday was cable’s most-watched non-sports telecast (4.84m).

In another big week on the political front, Fox News moved up to second among cablers in total viewers (2.4 million).