By Michael Hurley, CBS Boston

BOSTON (CBS) — NFL commissioner Roger Goodell didn’t really like seeing his face with a clown nose throughout Gillette Stadium on Thursday night. But he really didn’t like the information presented to him on Friday morning.

Ratings for the grand season-opening game between the Patriots and Chiefs dropped 12 percent from last year’s season opener between the Panthers and Broncos, according to Deadline.

Evaluating ratings can be a tricky endeavor. Yet one would think that the allure of the top two teams in the conference from last season facing off, combined with the star power of Tom Brady and Bill Belichick, would be enough to at least sustain last year’s ratings. Last year’s season opener featured the largely unknown Trevor Siemian taking the reins from Peyton Manning in Denver.

Making matters worse for the NFL? The ratings drop represents the fourth consecutive season opener to drop in ratings from the previous year, according to Deadline. It was the lowest rating for a season opener since 2009, according to SportsBusiness Daily.

As must always be stated in any story about these ratings, the NFL still remains head and shoulders above its competitors in terms of North American sports and television ratings in general across the networks. The NFL is still a very healthy league.

But the NFL doesn’t strive to merely remain healthy. It strives to dominate the globe. So any backward progress in terms of ratings will set off some alarms in owners’ offices and at 345 Park Avenue if the trend continues into the year.

Last year, the NFL used the excuse of increased interest in the presidential election drawing away attention from some of the league’s prime-time games. No ready-made explanation will be available this fall, so there will be some eager eyeballs in the NFL offices as the ratings numbers roll in over the next several weeks.