Professionally, among historians of the game, he is the greatest defensive end the National Football League has ever known.
Marchetti never went into a victory dance after making a tackle or a sack. Football was a team sport and, in his era, individuality repressed itself. Only the result counted; cheap acts of grandstanding were intolerable and rarely, if ever, occurred.
While attending a weekend reunion of Colts heroes in Ocean City, arranged, oddly enough, by a former Green Bay Packer, Tom Brown, for the benefit of a Salisbury youth fund, Marchetti was asked his views on an assortment of subjects.
Sacking the quarterback: "I wish they didn't count them because they aren't a true measure of what a defensive player does. I hate to see football become like baseball, a bunch of statistics.
"Suppose one end or a tackle is double- or triple-blocked. That means someone else gets the tackle or a sack. If a quarterback runs from the pocket and you take him down, that's a false sack. The player who pressured him is the one who made the play possible."
So, sacking the passer usually evolves from the collective contributions of teammates. That's Marchetti's reasoning for why generally happens.
The best tackle he ever faced? "That's easy. Forrest Gregg of the Packers. Not too big, but he knew what he was doing. Vince Lombardi said he was the best player he ever coached."
About Baltimore's fanatical love of football, particularly the Colts of the 1950s and 1960s, Marchetti explains how he remembers it: "It was special in our lives. We regularly had 57,000 or more in the stadium and I think I met them all at one time or another.
"I talked to Willie Lanier, the Kansas City Chiefs linebacker, at the Hall of Fame in Canton, Ohio. He came up and told me he was at Morgan State in Baltimore at the time we were playing and, to this day, he can't get over how the fans expressed themselves for all the Colts back then."
Was there any one player they put on a higher pedestal than the others? "Yes, Bert Rechichar. In those early years, he had the town in the palm of his hand. Raymond Berry, Lenny Moore, John Unitas, Art Donovan, Ordell Braase, Jim Mutscheller, any of them, will tell you the same."
Marchetti was asked to explain his little-known role in Don Shula's becoming coach of the Colts in 1963. Now, for the first time, he filled in the details.
"The year before Shula took over, we got hammered by the Chicago Bears. On Monday, I got a call to meet our owner, Carroll Rosenbloom. I thought maybe he was going to trade me. I felt so bad after the beating the Bears gave us.
"When I walked in the room, Carroll asked me why I was depressed. I told him because we lost. But he was smiling. Then he said, 'Don't worry; now I got my chance to fire Weeb Ewbank.'
"He asked me to recommend a coach. I told him Shula, who had played with us and was then a coaching assistant for the Detroit Lions. We were playing them the next week. A meeting was set up on the Saturday before the game between Rosenbloom and Shula.
"It was supposed to be secret. No one was to know. But Shula said he was working for George Wilson and, as the Lions' head coach, he wanted to tell him or he wouldn't go through with the idea. He informed Wilson. The meeting was then held and Shula, after the season was over, got the job."
What about Ewbank? "I thought he was the greatest judge of talent I ever knew," said Marchetti. "If he had a weakness, it was being too nice."
His vote for the toughest player of them all was a roommate, linebacker Bill Pellington. And the most talented? "Lenny Moore. He could do anything anybody does today and do it better. I used to tell him before games, 'Lenny, if you go, we go.' How true."
The current demand for autographs, for player jerseys and other memorabilia astonishes Gino. "I guess maybe I should have kept every shoelace, old socks and jockstraps if I had known things were going to be like this," he said.
Marchetti, 67, now a retired millionaire from the fast-food business, lives in suburban Philadelphia. But Baltimore, he says, "was the greatest time" of his life. L All because of his association with a certain football team.