Tom Thayer had played in enough football games that his mental archive of plays likely numbered in the thousands. He was an all-state offensive lineman at Joliet Catholic and an honorable mention All-American at Notre Dame. He played in the USFL for three years, then began an eight-year run on the Bears with the 1985 Super Bowl champions.

But while having lunch at Shaw’s Crab House in River North in January 1997, he was asked to describe one.

And it wasn’t just any conversation he was having. Thayer was being interviewed to be the Bears’ radio analyst. WMAQ had won the team’s rights from WGN, and operations manager Lorna Gladstone had narrowed her decision to incumbent Dan Hampton and Thayer. Play-by-play man Wayne Larrivee and analyst Hub Arkush were already set.

So, to gain a sense of what Thayer might sound like in the booth, she asked him to audition right at the table.

“She said, ‘Do a football play for me,’ ” Thayer said.

As if he were thumbing through a library card catalog, Thayer thought of a play from his past and described it in such detail yet in a manner understandable to Gladstone that it left an impression on her.

“It was a combination of faith and my enthusiasm for the opportunity and understanding how much time I was still studying football,” said Thayer, who had been spending lots of time at Halas Hall analyzing the Bears for Fox-32. “So I think that kind of caught her attention also.”

But just as one play doesn’t decide a game, Thayer did more to win the job. He showed personality, the ability to paint a picture in listeners’ minds and the desire to immerse himself in the job. Whereas Hampton would arrive on game weekends from his home in Arkansas, Thayer lived — and still lives — in Chicago.

“Tom has proven over and over again what you get from your color guy when he’s living and breathing all week long with the team,” Gladstone said.

Listeners can expect more of the same from Thayer on WBBM this season, his 23rd in the Bears’ booth, which began with the opening of training camp Thursday.

Fans attending practice might see Thayer, 57, observing from the sideline. What informs his thoughtful analysis are study habits akin to that of an honors student. Even when he’s not with the Bears, Thayer is watching them. He studies video as though he were still playing.

The habit was hammered into him by his offensive line coach with the Bears, the late Hall of Fame guard Dick Stanfel. After a broadcast, the game is loaded on Thayer’s iPad so he can break down and take notes on every play. He’ll watch it a second time, in addition to two or three games of the next opponent.

Playing guard in the NFL doesn’t attract the limelight, but Thayer might be benefitting from it more than ever as a broadcaster. With the potential of facing any defensive player during a game, whether pulling or picking up a blitz, Thayer had to learn about everyone on the other side of the ball. The knowledge gleaned in the trenches helps with his primary objective during a broadcast: explaining the success or failure of a play.

“That’s where the game is won and lost,” said play-by-play voice Jeff Joniak, who’s beginning his 19th season alongside Thayer. “Everything happens inside. I need to see it about five or six times, but he can see it instantaneously. It’s a gift to have that type of player next to you in the booth.”

Before Thayer was in the booth, he was on the outside as a listener. A longtime fan of talk radio — after all, he had a degree in media communications from Notre Dame — Thayer often listened to Steve Dahl and Garry Meier on WLUP during his playing days. Eventually, he became part of the show.

The relationship Thayer developed with management at The Loop led to a show he hosted with fellow Bears lineman Keith Van Horne in the mid-1990s, after they retired in ’93. It aired from midnight to 5 a.m. Their first guests: The Rolling Stones.

“Keith has a really good relationship with Keith Richards, and they were opening their tour in Chicago,” Thayer said. “We were broadcasting from The Loop, which was at the Hancock at the time, and they were staying across the street at the Ritz. So a couple members of the band came over, and then the rest of the guys were on the phone from their suite.”

The show didn’t last a year, but it wouldn’t be long until Thayer took the Bears’ analyst job. Despite his longevity in his second career, Thayer is driven by a fear of failure.

“It’s probably why I don’t have social media,” he said. “I’m too thin-skinned.”

Startling words from a member of the ’85 Bears, but when put into context, it makes sense. As a player, Thayer worked to earn the respect of big-name coaches such as Stanfel, George Allen and Mike Ditka. It was an endless pursuit, and he has carried that work ethic into broadcasting. And no amount of success is going to change that.

“I never in my life have felt that, OK, I’ve made it, I’m over the hump,” Thayer said. “I just live every day not wanting to fail. So you never stop. You just never stop.”