Monahan is the longest-tenured employee in the Yankees organization, having started his service to the club in 1962 as a bat boy and clubhouse attendant during his senior year of high school in Fort Lauderdale, Fla.
Monahan would ascend to the head athletic trainer post in 1973 after stops with several Minor League clubs, bearing witness to seven World Series championships and a historic succession of players passing through his office over a distinguished 39-year tenure.
"Gene Monahan embodies all the very best virtues that this organization strives to uphold," said Yankees managing general partner Hal Steinbrenner. "Gene has made a lifetime's worth of sacrifices and contributions in order to best serve the Yankees, and our entire organization will always be grateful."
Monahan missed part of last season undergoing treatment for throat and neck cancer, and he said that it forced him to reconsider his priorities.
"I had a big wake-up call, and I realized there's some other things in this life that I needed to do that are ... equally important," Monahan said.
Monahan said that he placed his trust in his doctors, fighting hard to rejoin the team as quickly as possible. He reclaimed his place alongside assistant athletic trainer Steve Donohue, who will succeed Monahan after this season.
"I came back a little prematurely, because I was tired and weak and didn't feel right," Monahan said. "It was good I came back, because the minute I left the house and was in the car, I felt better. When I got here, I felt like a million bucks."
But as Monahan pondered his future, he informed general manager Brian Cashman in January that he would not be returning after the season. Monahan kept it a secret from the players until Tuesday afternoon.
Unsure if he could get through a speech to the roster, Monahan instead buried his announcement at the end of a reminder about upcoming routine dermatological and oral cancer screenings after the club took batting practice.
"It was last-minute," Monahan said. "We got them all together, and I said, 'Here's what we're doing tomorrow, here's what we're doing the next day,' and my plan was to just say, 'Oh, by the way, this is my last season. Let's try to win this year.' And that was it."
So begins one of the final chapters in a big league life that began late in the 1972 season, when the Yankees needed some help from their Triple-A trainer to deal with a rash of injuries at Fenway Park.
"Of course, I was thrilled and scared," Monahan said. "I walked through that clubhouse door, and I was trembling. I knew what I was doing, but I was thinking, 'Please, not today. Don't anybody ask me to tape an ankle or anything.' I had no chance.
"But I walked through the door of the clubhouse, and back in those days, the guys carried around these big boom boxes. And Sparky Lyle had his right in the first locker there as I went across the room, and immediately, it relaxed me.
"He had Elton John on there singing, 'Get Back, Honky Cat.' I looked across the room, and he said, 'What are you doing there?' And I said, 'I don't know.' But he had that song going on, and I was OK."
And now, after giving attention to the Yankees for so many years, Monahan will focus on himself. He purchased a home in North Carolina, a happy medium between New York and Florida.
"I need to have a dog," Monahan said. "I need to have a house. I need to have a yard and a garden, maybe a pickup truck."
The fantasy Monahan holds is that after the season, he'll get behind the wheel and run a hand across the neck of that dog, whom he plans to name after NASCAR driver Ken Schrader -- auto racing being Monahan's other major passion in life.
"It's this little dream I thought of, saying, 'Hey, Schroeder, want to go down to the store? Get in the truck,'" Monahan said. "Pick up some grass seed or something. That would make me feel good. That and a cup of coffee. That would really make me happy, so that's what I'm going to do."
Monahan's eyes grow moist in the news conference room at Yankee Stadium. Describing himself as shy and introverted, he has probably already talked too much.
"I don't spend much time with the press," Monahan explains. "[Clubhouse manager] Pete Sheehy taught me that back in 1962. He said, 'You keep your ears open, your mouth shut, you'll be around.' I guess it worked."
Monahan excuses himself and returns to his office, hidden behind closed doors, where a Yankee or two will inevitably need to be looked at before the game. As always, Monahan has work to do.
"Until that last pitch is thrown this year, wherever that is -- hopefully it's deep into October or early November, we'll see," Monahan said. "I'll be there, being the biggest fan these players ever had, each inning that I'm out there. It's been a wonderful ride."