Keon, in 2016 voted by fans and a blue-ribbon panel as the greatest Toronto Maple Leafs player of all time, thinks it was in 1959-60, his final season in the Ontario Hockey Association, that he and two St. Michael's teammates were flattened by illness.
"Chicken pox or something was going through the (St. Michael's) school, and Bruce and Dave Draper and I all stayed at Jim's house for four or five days," Keon said from his Florida home. "He was trainer at the time, maybe working as assistant to (general manager) Father David Bauer, learning the ropes. The three of us called ourselves, 'the Gregory boys.'"
[RELATED: Gregory, Hockey Hall of Famer, former NHL executive, dies at 83 | Gregory 'was like a second father' to Hall of Famer Salming]
Keon's friendship with Gregory had taken root during the 1956-57 season, Keon's first as a St. Michael's center, Gregory tending to the bumps and bruises of the teenage roster.
Budding hockey executive Jim Gregory with the OHA junior St. Michael's Majors.
"Jim never sewed me up, but he took care of me," Keon said. "He studied. He was very curious, wanting to learn about injuries and how to help treat them. He worked very hard at it."
When Keon graduated to the Maple Leafs in 1960-61 and won the Calder Trophy as the top rookie in the NHL, so too did Gregory move up, named general manager of St. Michael's and winning the Memorial Cup that season.
Video: Former Maple Leafs GM Jim Gregory dies at 83
"On and off, I'd see Jim and his wife, Rosalie, when he moved on to the (OHA) Toronto Marlboros," said Keon, who kept in touch when Gregory won Memorial Cup championships in 1964 and 1967 with the Marlboros, then went west to coach the Maple Leafs' Western Hockey League affiliate in Vancouver in 1967-68.
Gregory returned to Toronto in 1968 as a scout, then was promoted to GM in 1968-69, a job he held for 10 seasons. He named Keon captain of the Maple Leafs for the start of the 1969-70 season, succeeding George Armstrong. Gregory went into the team's Maple Leaf Gardens dressing room to give Keon the news and a jersey bearing a freshly stitched "C."
Dave Keon in the late 1950s with the OHA St. Michael's Majors.
"Jim worked really hard, he was always trying to learn," Keon said. "As a trainer with St. Michael's, he learned from (coach) Bob Goldham and Father Bauer. And Jim also learned on his own, when he was at different levels, how to handle people and get the most out of them.
"He got the (GM) job with the Leafs, and I thought he did a really good job. They did some really good drafting. The Montreal Canadiens, mid-1970s and on, it was a difficult task trying to beat them.
"The Leafs didn't get it done, and the owner (Harold Ballard) was a little bit different. Jim was managing with one arm tied behind his back and someone looking over his shoulder. You can't do the things you want to do that way. From that standpoint, Jim was handcuffed, as simple as that."
Indeed, it was while vacationing at his cottage following the 1978-79 season, the Maple Leafs having been eliminated in the Quarterfinals by the Canadiens, that Gregory learned that Ballard had fired him.
The news came when Montreal-based NHL executive vice president Brian O'Neill phoned him to gauge the now-former Toronto GM's interest in a job with the League.
The 1969-70 Toronto Maple Leafs, GM Jim Gregory front row, far left.
"I told Jim that I thought that he had other opportunities to be a GM, but I don't think he wanted to leave Toronto," Keon said. "But he got what was probably a better job, working with the NHL."
A trailblazing GM in Toronto, among the first to tap Europe for talent, Gregory became an influential League executive for four decades, pioneering the use of video to review goals while engineering an expansion of the NHL Central Scouting Bureau.
Gregory was involved in every level of the game almost his entire life, serving as chairman of the Hockey Hall of Fame selection committee from 1998-2014 -- except for 2007, the year he was elected to the shrine in the Builders category.
Video: Teams around the NHL pay tribute to Jim Gregory
Gregory left an imprint on many of the players who played for him with the Maple Leafs during his run as Toronto general manager from 1969-79. To that end, former Leafs Darryl Sittler, Dave "Tiger" Williams and Lanny McDonald all visited their ex-GM during his recent hospital stay.
"He always looked out for us," Sittler said from Florida on Wednesday. "He cared.
"There's not many people who you can say you've been friends with for almost 50 years, but that was the case with Jim."
Sittler chuckled about an incident that occurred shortly after he was selected No. 8 at the 1970 Draft by the Gregory-run Maple Leafs.
"I was engaged at the time to my future wife Wendy," Sittler recalled. "Jim looked at me and said: "Why would you want to get married when you have the world by the tail right now?
"Jim ended up appreciating Wendy for the great person she was. And for subsequent years he'd always come up to us and say: 'My comments I told you about why you'd want to get married, well, that may have been the stupidest goofiest thing I've ever said.'
"A special man."
Hockey Hall of Fame selection committee chairman Jim Gregory and Hall chairman Pat Quinn drop a 2013 face-off between Darryl Sittler (left) and Lanny McDonald.
Today, if Keon wanted all to know what Gregory represented, from sharpening skates with St. Michael's to working in the NHL executive suites, it's that "he was a man who started at the bottom and worked his way to the top. He was always learning. Jim tried to be the best general manager that he could be. He tried to give the Leafs direction. He was a Maple Leaf. Jim really cared about their success, and he cared about the success of all the players on the team."
NHL.com staff writer Mike Zeisberger contributed to this report
Photos: Hockey Hall of Fame Images