ENGLEWOOD, Colo. -- The recipe for the storybook ending of Peyton Manning’s Hall of Fame career included a long list of ingredients.

The league’s No. 1 defense, the Broncos’ prowess in close games that resulted in 11 wins by seven or fewer points, Brock Osweiler’s work in relief of an injured Manning, and a tough-minded, no-nonsense locker room.

Oh, and one extended middle finger and a set of orthotics a guy built in Manning’s garage.

Just all part of the tapestry in what became the "most unique" season of Manning’s career. A career Manning finished Monday, retiring after 18 NFL seasons that will land him in the Hall of Fame as soon as the five-year waiting period is over.

Manning had far better seasons, with more touchdowns and more signature moments, than his last. Manning was leading the league in interceptions when he was pulled from the Broncos’ Nov. 15 loss to the Kansas City Chiefs. It was painfully obvious the pain in his left foot had become too much for him to play.

At that moment 2015 became a season unlike any other for Manning at a time when he was clearly aware his career clock was loudly ticking. Broncos coach Gary Kubiak, as part of his reminiscence Monday, said Manning was not happy with the message that followed that game.

"“He and I had some tremendous meetings, interesting moments along the way," Kubiak said. "We were 7-2, we had had a rough day against Kansas City. I knew he wasn’t feeling good, I knew his foot was hurting. I said, 'You’re going to get healthy.' He was not real happy with that."

From there Manning went to North Carolina to see Dr. Robert Anderson, had a cast placed on his injured foot, had the cast removed after two weeks and started on a rehab program that included solitary throwing sessions, away from the team, with practice squad wide receiver Jordan Taylor, assistant equipment manager Mike Harrington and rookie tight end Jeff Heuerman, who was on injured reserve.

Day after day, the Broncos went about their business and Manning went about his.

This is also the time that Manning’s agent, Tom Condon, located someone who made orthotics for those with similar foot injuries to Manning’s plantar fascia injury. The orthotic is heated to bond with the shoe.

Manning said they built three in his garage and fused one to a pair of dress shoes -- the shoes he was wearing Monday -- one to a pair of sneakers, and one in a pair of cleats. The same pair of cleats he wore in all of his rehab workouts, the regular-season finale, and all of the Broncos’ playoff games, including Super Bowl 50.

Manning said his foot felt better when he wore the orthotic and eventually those rehab workouts got better, as he could throw with more weight on his left foot. As the regular season drew to a close and Manning was still relegated to his throwing sessions in the team’s indoor complex, his frustration finally bubbled over, hence his middle finger "salute" to Kubiak.

"I think there were two weeks left in the regular season," Kubiak said. "And as I’m watching the film, there was something different about the workout. During the workout he sent me a signal, to the film -- 'Hey, you’re No. 1.' You could take it that way. I took it as 'I’m ready to play.'"

Kubiak called Manning on the drive home that night and said, "Hey, workout looked great and, oh, by the way, I got the signal."

For Manning’s part, he just smiled and said, "I can’t confirm that."

Kubiak decided then Manning would be back in the lineup and confirmed it after an emotional conversation with the quarterback the next day. But while it is all just a small slice of a Hall of Fame career, for Manning’s desire to return to be so strong -- after he had already come back from spinal fusion surgery to play in Denver -- was a fitting exclamation point on his career.

And the Super Bowl win last month simply became the bow that tied it all up.

What comes next? Even Manning said Monday he doesn’t know, though he's optimistic it will be something he's passionate about.

"I believe it," Manning said. "I’m not shrinking from life."

"I have the utmost respect for him, the utmost respect," Kubiak said. "It was only nine months for me, but I’ll remember it for a lifetime."