Looking for the next big short? Put the National Football League on the list, according to best-selling author Michael Lewis.

Lewis, the author of influential sports business books turned movies including “The Big Short,” “The Blind Side” and “Moneyball,” stopped by Yahoo Finance on Tuesday to discuss his latest book, “The Undoing Project.”

On our afternoon live show The Final Round, we asked Lewis what part of the market might become the next “big short.” He was hesitant to answer, saying, “You’re asking the wrong person. Everybody will be a little stupider, if I answer that question. Can I answer this way: When people roll in with some big prediction, and they actually seem really certain about it, be very suspicious of them… When people come at you and say, ‘Oh, this is the short,’ it’s an interesting exercise, but the more serious they are about their prediction, the less seriously you should take them.”

But after the live show, Lewis thought of the NFL: “The NFL has real business problems. The CTE issues… I’ll give you the next short: the NFL.”

It’s an interesting thought: after the league has weathered so many scandals and PR issues over the last few years, from head injuries to domestic violence cases to political protests, might this season truly be the beginning of a decline for football? To put it in Wall Street terms: the NFL has enjoyed a long bull market, and bull markets eventually come to an end.

As of the halfway point of the current NFL season, television ratings are down an average 5% compared to the same point last year, and nearly 20% from 2015. NFL sponsors are reportedly “nervous” amidst the ratings dip and the ongoing political controversy, and at least one, Papa John’s, has publicly said it will pull back on its NFL advertising.

Lewis, an influential thinker on sports leagues and their finances, may be on to something. On the other hand, he added that practically speaking, he’s not sure how a person would go about shorting the NFL just yet.

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Daniel Roberts is the sports business writer at Yahoo Finance. Follow him on Twitter at @readDanwrite. Sportsbook is our sports business video and podcast series.

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