(AP Photo/LM Otero)

Last season’s inaugural College Football Playoff semifinals drew mammoth ratings for ESPN, with the Oregon-Florida State and Ohio State-Alabama games each garnering more than 28 million viewers, the biggest cable-television audiences ever — at least until 11 days later, when the championship game between Ohio State and Oregon drew 33 million viewers to become the most-watched cable program in the history of television.

ESPN was able to crow about this ratings bonanza for a few days, until thoughts turned to the 2015 season and people became attuned to the fact that things were about to get a whole lot different.

Last season’s semifinals were on New Year’s Day, a day that’s been intertwined with college football watching pretty much forever. This year’s semifinals — Clemson-Oklahoma and Alabama-Michigan State — are not, instead moving to New Year’s Eve. It’ll be like that again in 2016, and 2018, and 2019. Basically any season in which the semifinals aren’t played in the Rose and Sugar bowls, which are contractually tied to New Year’s Day.

And there has been much teeth-gnashing and rending of garments. New Year’s Eve is for parties, and for watching a ball drop in Times Square, and for making questionable life choices involving bottom-shelf Champagne. Rarely has it been devoted to serious college football consumption. People got upset about this.

But the College Football Playoff honchos were unmoved. They see a chance to start a new tradition on New Year’s Eve, even if fewer people will watch the games because they are out doing typical New Year’s Eve things.

ESPN reportedly lobbied College Football Playoff officials to change the semifinal date to Jan. 2, which makes a certain amount of sense this season: It’s a Saturday, and there’s no competition from the NFL. But their pleas were turned down.

“We were too close into the window of time for things to change with buildings, venues, all that stuff,” Burke Magnus, ESPN’s executive vice president of programming and scheduling, told Ad Week.

In any case, the lower TV ratings probably aren’t even going to bother ESPN all that much, even if it is paying $7.3 billion over 12 years to carry the playoff games. As television consultant Kevin O’Malley told Sports Illustrated’s Pete Thamel, ESPN already has your money in the form of subscriber fees, meaning the ratings don’t mean as much to them as they would to one of the big-four networks. Plus, O’Malley said, advertising packages for Thursday night’s game already have been purchased.

“Individual ratings of games are not as important,” O’Malley told Thamel. “Years ago getting a 14 or a 15 rating was critical. Now it’s not.”

Added Ilan Ben-Hanan, vice president for college sports programming at ESPN in a conversation with the New York Times’ Richard Sandomir: “We realize that New Year’s Eve is not New Year’s Day. We know it’ll be different. But we think the notion of sports and a holiday can exist peacefully.”

But no question, the television audience will be smaller. Thursday’s first semifinal between Oklahoma and Clemson starts at 4 p.m. EST. People will still be at work, especially on the West Coast. The second game between Alabama and Michigan State is slated to kick off at 8:10 p.m. EST, right when people in the east are heading out to do whatever they do on New Year’s Eve. But it’s probably not going to be enough to get playoff officials to alter their plans.

“The games are sure to take a measurable hit versus last year, but all other things being equal I think both games would still average well over 20 million viewers,” Robert Seidman, co-founder of the ratings site TV by the Numbers, said in an e-mail response to questions submitted by The Post. “All other things aren’t equal, though, and I don’t think the Oklahoma vs. Clemson game would’ve done as well as last year’s Oregon/Florida State matchup even if it aired on New Year’s Day. Even people who didn’t care about college football knew who Jameis Winston was. Do casual college football fans know many players on Oklahoma or Clemson?”

Seidman’s prediction: Oklahoma-Clemson will draw 19.5 million viewers (about a 30 percent drop from the first game last season), and Michigan State-Alabama will draw 23.5 million viewers (about a 16 percent drop from the second).

While ESPN may be outwardly unworried about a possible ratings plunge, that hasn’t stopped the network from creating an advertising blitz featuring Jimmy Kimmel and a number of other famous and semi-famous names, a campaign that began months ago.

And, as noted Wednesday by Deadspin’s Timothy Burke, ESPN parent company Disney also has been putting College Football Playoff Easter eggs into its “General Hospital” soap opera on ABC. Look carefully in the background at around the 50-second mark of this preview.

So concern about ratings exists. You just have to look for it.