There were mitigating circumstances, but the New York Rangers and the Philadelphia Flyers combined to produce the lowest Winter Classic overnight ratings since the NHL started the gimmick game.

From the Puck The Media:

According to Sports Business Daily (reg. required), NBC drew a 2.4 overnight rating. While this is still more than double what any indoor hockey game would draw and very solid for any January 2nd NHL game, this is the lowest overnight rating for any of the first five, and down 15% from last year's primetime edition of the game. The game faced heavy competition, including the Outback Bowl on ABC, which drew a 5.0, and the 9.0 overnight for the Rose Bowl on ESPN.

Winter Classic Overnights

2008, Pittsburgh vs. Buffalo, 1/1/08: 2.6
2009, Detroit vs. Chicago, 1/1/09: 2.9
2010, Philadelphia vs. Boston, 1/1/10: 2.6
2011, Washington vs. Pittsburgh, 1/1/11: 2.8
2012, NY Rangers vs. Philadelphia, 1/2/12: 2.4

The NHL probably isn't going to give a rat's patootie about these ratings. The Jan. 2 date (a Monday afternoon) and the shift in start time provide enough cover for the drop in viewership.

If there's any lesson to be learned here, it's the venue still matters: Wrigley and Fenway mattered; Citizens Bank Park didn't. If nothing else, it's an argument for The Big House over Comerica in Michigan. And for the League to get a little adventurous in its booking for 2013: As we said this morning, pop the Toronto Maple Leafs or the San Jose Sharks in the game.

But again: This game is increasingly becoming un-tethered to its TV ratings, like the All-Star Game has. It's all about the revenue generated onsite and online, and the fact is that the Flyers and Rangers drew over 45,000 fans for an alumni game and for the Winter Classic, and those fans purchased swag on Black Friday levels during the last few days.

There are reasons for this ratings drop; the Winter Classic being on the decline isn't one of them, at least in the metrics the NHL cares about.

UPDATE: Some decent news for the NHL to spin, via Neil Best of Newsday and Steve Lepore: "Winter Classic averaged 3.74M viewers, fourth best among the five played to date, but better than last one played in afternoon in 2010."