Given back his job as starting quarterback, Peyton Manning stood inside the Broncos’ locker room and revealed a little of what’s inside his heart. There is gratitude for his last, best chance to win the Super Bowl one more time. But the hurt also lingers, as the result of pain that struck Manning so many ways during the 2015 NFL season that he never saw it all coming.

“There were a lot of firsts, a lot of firsts for me this year. It’s weird in your 18th season to have so many firsts. But when you sign up to play, you sign up for everything,” Manning told me Thursday, after Denver coach Gary Kubiak announced the 39-year-old quarterback would start ahead of Brock Osweiler in the playoffs.

Manning looked me in the eye and made a confession: Nothing in his long and brilliant professional career prepared him for the adversity that blindsided him in the past year. It shook a quarterback whose reputation is built on controlling the game’s chaos.

“You learn about yourself and how you handle it. That’s been my theme all year: Just keep being a pro. I’ve been through a lot of stuff … but that’s what I drew on during this time: Be a pro. Handle it. And keep the faith,” Manning said.

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“There’s no guarantee what’s going to happen, and you have to be willing and prepared for anything. I’m sure every head coach that signs up thinks he’s going to win division titles and Super Bowls, and then all of a sudden something bad happens, and you get fired after two years. When you sign up to play, you sign up with everything that comes with it. That means getting injured and the changes and dealing with everything.”

Manning had to deal with a ton. And it hurt like a ton of bricks.

His salary was cut. His favored offensive scheme was junked. His touchdown-to-interception ratio stunk. His foot hurt. His coach benched him. Football analysts declared Manning washed up, and fans booed him in his home stadium. His reputation was attacked by media reports that suggested Manning would be a malcontent in a backup role and linked his family to human growth hormone, with him angrily denying the implications he used HGH.

The adversity was stacked high. Yes, Manning admitted, it tested his professionalism to the max, in ways never before experienced. He missed six contests because of a partially torn plantar fascia in his left foot. His 67.9 quarterback rating, as well as his 224.9 yards passing per game, were the worst marks of his career. In the end, football finds a way to humble everybody, even a five-time MVP.

“I’ve always told you all I’ll never write a book,” Manning said. “I could probably write a pretty good short story, though, on this past offseason and this season. But, right now, it’s fun to focus on the now.”

During the 27-20 comeback victory against San Diego that re-established Manning as the starting quarterback and allowed Denver to secure the No. 1 seed in the AFC for the playoffs, he got crushed in the chest by Chargers defensive tackle Damion Square. The veteran QB winced and got back up. But, come to think of it, taking wicked hits and refusing to quit has been the recurring story of his 18th pro year.

“A drama,” Manning said.

I suggested it could be written as a grand soap opera, like the HBO television series that told the tale of Enoch “Nucky” Thompson and was watched religiously by Manning from 2010-14: “Boardwalk Empire.”

“Now that,” Manning said with a grin, “would be an insult to ‘Boardwalk Empire.’ “

Through the years, Manning has learned to defuse the pressure of playing quarterback with the same sense of humor that has drawn rave reviews on “Saturday Night Live.” But, as a man who often seems compelled to set the agenda, he seldom shows vulnerability. His every comment is on-point, and as rehearsed as a timing route he perfects with 1,000 throws at practice.

One dead giveaway to the rare times when Manning reveals a little of what makes him tick, however, is a slight stammer in his speech, which only seems to happen when he’s working out an idea for the first time. Maybe, just maybe, the veteran quarterback let some unfiltered truth slip, when he walked away from the crush of cameras encircling his locker, and he stopped me to add a few details of how the hard hits of this long, strange season have left a few dents in his heart.

Although another season remains on his contract, it’s hard to imagine Manning in training camp with Denver this summer. He can count on no more than three more games with the Broncos, which is what the team needs to win the Super Bowl.

I asked Manning: Does this feel like your last rodeo?

“I’d be lying,” Manning said, “if I said I’m not thinking about that.”

Win the championship ring, and all the hurt of the 2015 NFL season fades away.

Mark Kiszla: mkiszla@denverpost.com or @markkiszla