In this day and age, I approach the whole notion of rivalries with cynicism; they seem like a marketing ploy brought to you by the same people who tried to sell you tickets to the Home Run Derby during All-Star game week. (Really, I mean, why should we pay top dollar to watch what amounts to nothing more than a glorified batting practice?)

These days the league’s talent pool is too watered down, and teams don’t face each other often enough to develop serious feelings toward one another. It was a different story in an eight or twelve team league playing 154 game seasons. Today, moreover, players switch allegiances too readily for true rivalry to flourish. Opponent today, teammate tomorrow.

Rivalry is a fan thing. Once a Red Sox fan, always a Yankee hater, and vice versa. Those feelings last a lifetime. The wounds inflicted by a Bucky Dent or an Aaron Boone don’t heal.

I first thought about this subject when the Players’ Association nixed a deal that would have sent Alex Rodriguez from the Texas Rangers to the Boston Red Sox. Rodriguez was subsequently dealt to the New York Yankees. Did he care one way or the other? If so, I’m guessing it was only because of off-field considerations: he’s a native New Yorker and, say all you will about Boston, the night life’s better in the city that never sleeps.

Furthermore, as far as direct rivalry goes, it is clear to the objective observer that the Yanks are, historically, far and away above the Bosox. Even forgetting all those championship seasons in the Bronx since Boston last won a World Series, this year they’ve built up an eight game lead after playing only 100.

But, as I look down from the press box upon a virtually empty Olympic Stadium, awaiting a meaningless late July contest between the fifth place Expos and fourth place Mets, I realize the one factor that engulfs a game between rivals: fan energy. Face it, there’s more excitement in my living room when the Red Sox play the Yankees on television than there is here in the Stadium tonight. It is simply impossible not to care when you’re in front, or in the midst, of 50,000 at Yankee Stadium or 35,000 at Fenway Park—standings amongst people who care passionately, like they care about few other things in their lives.

That’s why you see Derek Jeter flying five rows deep into the stands to catch a pop fly. That’s why you see almost teammates A-Rod and Jason Varitek get into a brawl. That’s why the home-and-home series these teams will play against each other come September will be the most exciting baseball of the stretch drive, regardless of the standings.

Though the fans sometimes appear to be the forgotten part of the pro sports equation, they are in fact the source of its intensity. Unless they buy into the fiction that sports matter, the whole enterprise collapses—which is exactly what has happened in Montreal, where people don’t care anymore.

The fans decide what matters through the simple act of participation. That’s the bottom line—both figuratively and literally.

Creating the idea that the games matter is no simple marketing ploy. In baseball, it goes deeper than that. It’s about building a genuine loyalty. It works in places like Boston, New York, Chicago and St. Louis because the fans’ affiliations to their teams transcend their affection for any single player or even for the thrill of victory. It’s about history, and parents teaching the game to their children. It’s about tradition. And it’s about being a part of something big and important, something you share with friends and community. It’s something to envy.