During his first season as the play-by-play voice of ESPN’s “Monday Night Football,” Sean McDonough would occasionally appear on camera, as play-by-play announcers are known to do. And viewers would occasionally be fixated not on McDonough and his partner, Jon Gruden, but instead on the giant piece of paper in his hand. It got to the point that lead “MNF” producer Jay Rothman told McDonough the sheet was a distraction, that viewers were staring at that instead of at the broadcasters, and that he needed to please put it down.

What was McDonough holding? What will he be holding tonight, when the Redskins face the Eagles on “Monday Night Football”? What purpose does it serve? Where does it come from?

As it turns out, he’ll be holding his spotter chart, something used by virtually every television broadcaster to help them follow the action and correctly call a game while adding insight and statistics and context. And McDonough’s version — two 11-by-17 pieces of card stock taped together, with computer-generated data and hundreds of handwritten notes — comes from Harrisonburg, Va., and a man who now makes a living providing these cheat sheets to football broadcasters.

Just when you think you know this industry, you stumble upon something you’ve never heard of: Tony Britt’s Spotter Charts.

Come again?

Broadcasters have long used spotter charts, both as a personal cheat sheet and as a guide for their spotter to tell them who carried the ball, who recovered a fumble, who made a tackle, who blocked a kick. As long as the broadcaster and spotter are working off the same chart — players in the same place, positions in the same format — they can communicate instantly and accurately without viewers even knowing a spotter is involved.

McDonough, like everyone else, used to make his charts by hand, on manila folders, a process that sucked up hours each week: finding names and numbers, heights and weights, schools and stats, and writing them onto folders he could use during the upcoming game. Then he discovered one of the nichest of all niche industries: folks who would make a chart for him. And then, at an ESPN summit, he found Tony Britt.

Who’s Tony Britt? 

He isn’t the only guy in this industry, but he’s a big player. He used to make charts for Brent Musburger. He sends them each week to Chris Spielman and Mark Schlereth, Bob Wischusen and Steve Levy, Eli Gold at the University of Alabama and Tony Caridi at West Virginia, Andre Ware and Mack Brown and Danny Kanell and about 100 announcers in all, including the voice of “Monday Night Football.”

Britt has gone through plenty of careers: a VP of communication, an employee of the U.S. Olympic Committee, a communications director for an athletics group, a GM of a weekly newspaper, an investment adviser, a ski instructor, a sports copy editor, a stay-at-home dad. He’s also been an independent contractor with ESPN for more than three decades, serving as a game-day statistician, sitting next to broadcasters across the country and feeding them facts and figures.

About a decade ago, he was sitting next to Pam Ward, and he heard her complaining about her spotter charts: that they were outdated, hard to read and late arriving.

“And I said, ‘Well, I think I could do that better,’ ” Britt recalled. He made her a sample using Microsoft Office, and then he became her supplier. Another broadcaster saw Ward’s charts and wanted the same, so Britt’s business was formed.

That lasted for a few years; each chart would take him six to eight hours, even using technology. Then, in 2012, Britt moved with his wife — JMU communications professor Lori Leonard Britt — to Harrisonburg, and met Morgan Benton, a professor in JMU’s Department of Integrated Science and Technology. Benton brought some programming students to Britt, and together they began dreaming up a way to automate the creation of the spotter boards.

By the fall of 2012, the software they created together was strong enough to use, streamlining a balky process. By 2013, they were sending out fliers and had 15 to 20 customers. After Britt was invited to an ESPN college football broadcasters summit — where he met with McDonough — his clientele more than doubled.

Business kept booming, and now one of those former JMU students (Adam Maas) is a minority partner, and they have 16 seasonal contractors who spend the fall churning out charts complete with rosters, statistics, depth charts, injuries, transactions and everything else. Britt works 70- or 80-hour weeks in the early fall, from Sunday afternoon through Thursday morning, creating spotter charts for games he will never watch. (He doesn’t have cable.)

How valuable are they to broadcasters?

“It’s an invaluable service,” McDonough said. “I shouldn’t say that; he’ll probably charge ESPN twice as much now.”

But McDonough was serious. The PDFs of his charts are available by Wednesday morning each week; he either goes to pick them up at a local copy store or has them delivered to his location. He marks them up with his own information, gives a duplicate copy to his spotter and uses all the hours he used to spend doing arts and crafts work watching tape, or reading articles, or otherwise preparing for his actual job.

I mean, I used to spend hours and hours and hours every week just getting the names, numbers, heights, weights, home towns, colleges, stats, all on paper,” McDonough said. “And it didn’t look anywhere near as good as what comes on Tony’s boards every week. . . . I just like everything about it — and I’m not trying to drum up business for him. I met the guy once in my life. I just think it’s terrific.”

Wait, how much do these things cost anyhow?

That’s proprietary. But it’s enough that the business is now Britt’s full-time job. The prices are variable based on the outlet; he gives them to young amateurs for free and charges as little as $50 for Division III broadcasters. The rates are higher if you’re an ESPN or a Fox.

And they’re all the same?

Of course not. McDonough likes two 11-by-17 sheets taped together, with the offense on the bottom facing the defense on the top, and the lines closest to the tape. (Both sheets are two-sided.)

Some broadcasters prefer a one-page front-and-back chart. Some like to tape them side-by-side, and some like to tape them to the booth window. Some like the players grouped by numbers, and some by depth chart. Some like receivers split wide, and some like them grouped together. Some like the quarterback in the center, and some like the quarterback off to the side. There are at least 10 standard variations.

There are also at least two other competitors with similar businesses. Who knew, right?

And where do they wind up after the game is over?

Well, McDonough kept his charts for years, as mementos of his career, but then an anti-hoarding consultant who was helping him reduce clutter recommended he trash all his old boards. He regrets the decision.

Still, as a season goes on, he will bring old charts into the booth with him, so he can transcribe old notes and use nuggets he never had a chance to reference and generally call the best game he can. As long as he keeps them all off camera.

“Gruden said last year that my spotter board was bigger than Andy Reid’s play-calling sheet,” McDonough said. “But there are certain tidbits or stories or stats that you want to get in during the game, and you want to report accurately, and you can’t memorize all those things. So you need to have someplace to put them where it’s easily accessible. . . . It’s an important part of what we do, that’s for sure.”

Weird, right?

“I don’t think people have any idea,” McDonough said.

The irony is my MBA thesis was on becoming a sports media consultant, but the path that got me here is far different than I imagined, and the environment and the role I play is drastically different than anything I imagined,” Britt said. “I’m blessed and grateful all the time.”

Read more from The Post: