Repeats of its “CSI” franchise and a lengthy NFL overrun on Sunday lifted CBS to a primetime victory in key demos in one of the least-watched frames of the year.

The four major broadcast nets combined for an average audience of 28 million viewers during primetime, down sharply from the previous week’s 40 million and easily the smallest tune-in since late August.

Week featured a smattering of firstrun programs, especially early in the week, but consisted almost exclusively of repeats and annual holiday movies the rest of the way.

In a rarity, a cable program — ESPN’s “Monday Night Football” between the Indianapolis Colts and Cincinnati Bengals — stood as the top demo draw for the week, averaging a 5.6 rating/15 share in adults 18-49 and a 5.9/15 in adults 25-54.

It was also the No. 2 telecast in total viewers (14.22 million), lagging only NBC’s original edition of “Deal or No Deal” on Monday (15.37 million).

According to in-home viewing estimates by Nielsen, CBS finished on top for the Dec. 18-24 frame with a 2.5 rating/8 share in adults 18-49, followed closely by NBC (2.4/7). ABC and Fox tied for third (2.0/6), with Univision fifth (1.4/4).

The Eye also won in adults 25-54 (3.1/9 to 2.8/8 for NBC) and remained perfect for the season in total viewers (8.9 million, vs. 7.3 million for runner-up NBC).

Repeats of all three editions of the “CSI” franchise ranked among the week’s top 10 shows in both demos and total viewers, with Thursday’s original (3.8/11. 12.95m) and Wednesday’s “NY” (3.8/11, 12.14m) both winning their timeslots with ease.

What put the Eye over the top, though, was Sunday’s 45-minute NFL overrun (6.9/29 in 18-49, 20.52m) as both the Denver-Cincinnati and San Diego-Seattle contests went down to the wire.

NBC played some games of its own during the frame, with Monday’s “Deal or No Deal” (4.4/12 in 18-49, 15.37m) and the premiere of the new “Identity” (4.4/11, 12.26m) tying as the No. 2 program for the week in 18-49.

“Identity” won four of its five nights, with its best numbers after its Monday bow coming on Wednesday (3.0/9, 8.76m). Show is a candidate to return at midseason (Daily Variety, Dec. 27).

ABC had another quiet week, with its few firstrun programs — including Monday drama “What About Brian” (2.0/5, 4.58m) and Tuesday comedy “Big Day” (1.8/5, 5.06m) — failing to make much noise.

Net was the leader on Saturday, though, with its annual airing of “The Sound of Music” (2.4/8, 8.34m).

Fox was paced by Tuesday’s repeat of “House” (3.9/10 in 18-49, 10.11m), the week’s No. 1 scripted telecast among adults 18-49. Among firstrun shows, “The War at Home” (1.8/5, 4.32m) didn’t do a whole lot on its new night, Thursday, but it did retain nearly all of its lead-in from “‘Til Death” (1.9/6, 4.94m).

Univision’s “La Fea Mas Bella” averaged 1.8 million adults 18-34 in the 8 o’clock hour from Monday to Friday to beat all of the major nets.

ESPN dominated the week in cable thanks to “Monday Night Football” and a college football game on Sunday between Hawaii and Arizona State (1.2/4 in 18-49, 3.50m).

Of note on Christmas Eve was the start of TBS’ 10th annual “24 Hours of A Christmas Story,” as the first of 12 airings of the popular pic averaged a sturdy 1.8/6 in 18-49 and 4.74 million viewers overall from 8 to 10 p.m. The second airing also did well from 10 to midnight (1.6/7, 3.58m).