Mara, 55, is team president and chief executive, having succeeded his father, the venerable Wellington Mara, as patriarch of one of the NFL's flagship franchises. His life has been consumed with pro football, even during his years as a New York lawyer.
As Wellington's oldest son and a former Giants ballboy, Mara lived through the team's darkest days. He suffered through the chants of "Goodbye Allie" when coach Allie Sherman was vilified in the 1960s. Watched in dismay as former Giants assistants Vince Lombardi and Tom Landry grew into Hall of Fame coaches in Green Bay and Dallas while the Giants floundered. Was an eyewitness to "The Fumble" in 1978. Saw the plane fly overhead three weeks later carrying the banner "15 years of lousy football. We've had enough."
So when you read Mara's quote in the wake of Sunday's meltdown in Minnesota, which came a week after an embarrassing Giants Stadium farewell against the Panthers, you'll have a sense of how deep his angst and anger ran.
"Probably as disappointed as I have ever been in my life with this team, given the expectations that we had this year, given the roster that I thought we had and given the way we started out, and given the embarrassment of the last two games."
Mara has been a bubbling cauldron since the Giants suffered one of the most calamitous finishes in their history after a 5-0 start. He finally let it all out Monday in one of the most brutally honest diatribes ever delivered by a team owner. He skewered what was easily the NFL's most disappointing team this season. No one was more disconsolate than the owner, who echoed the dejection of the fans.
"I'm disappointed in everything," he said. "I'm unhappy at everybody. It is just not acceptable to perform like that. There are 8-8 seasons and there are 8-8 seasons. This one felt a lot more like 2-14 to me."
A team that once had legitimate Super Bowl aspirations withered, playing some historically bad defense. Under coordinator Bill Sheridan, the Giants allowed 427 points, the third-highest total in the NFL behind the Rams and Lions, teams with three wins between them.
In their first five games, the Giants allowed an average of 14.2 points; in the final 11, that figure ballooned to 32.4. They surrendered at least 40 points five times - including the last two games. It was their most points allowed since the 501 in 1966 in a 14-game season.
Mara knows about that 1-12-1 debacle; he was 12 years old and often would be driven to tears by the taunts of his classmates. Forty-three years later, the tears are gone. The rage still simmers.
"I have been around a long time, and I thought I had seen everything," he said. "But I certainly didn't see this coming, and I certainly didn't see the last two weeks coming.
"We always used to pride ourselves on being a tough team, both physically and mentally. I didn't see any evidence of that over the second half of the season."
Within hours of Mara's harangue, coach Tom Coughlin fired Sheridan, a widely expected move. Coughlin is not in danger of losing his job, not after winning the Super Bowl only two years ago. But the importance of hiring the right defensive coordinator to replace Sheridan cannot be underestimated.
You can't directly blame Coughlin for Sheridan's shortcomings, but you can blame him for making the wrong hire. Mess this next one up, and Mara soon might express his outrage by showing Coughlin the door.