Tim Wendel’s baseball novel, “Castro’s Curveball,” tells how an aging minor-league catcher discovers a 20-year-old pitching ace in a Havana slum in 1947. The young Fidel Alejandro Castro Ruz has a breaking ball that drops like it rolled off the table. But young Castro is distracted by big crazy dreams.

The tale unfolds into a vivid intrigue about what woulda, coulda, shoulda been if that pesky Cuban revolution hadn’t gotten in the way — and that potential baseball prodigy named Castro hadn’t decided it was his destiny to lead it.

Coincidentally, Thursday was the 57th anniversary of the embargo on U.S. exports to Cuba. Back then, there was no question that socialism and capitalism could not coexist.

And baseball is a pedigreed offspring of capitalism — that’s the contention of purists who love the sport, or at least it ought to be their contention.

That’s why fans should be wary as they digest proposed changes reportedly under discussion between Major League Baseball owners and the players union. The proposals vary from fewer mound visits, to imposing the designated hitter in the National League — the DH has been an American League exclusive, in effect since 1973, almost as long as the Cuba embargo — and (get this) starting extra innings with a runner on second base.

Commissioner Rob Manfred has a reputation for pushing anything that will speed up the game. But extra-inningghost runners? That’s no longer baseball.

On the other hand, this is exactly what the purists have argued for years about the designated hitter — it’s not baseball. But for many years the player’s union has backed the adoption of a universal DH in both leagues, with the belief that the DH jobs would go to veteran hitters at higher salaries. The owners in the National League have resisted, even though colleges have abandoned at-bats for pitchers, and National League pitchers hit an all-time low .115 average last year.

Purists regard the baseball rule book very much as a tea partier regards the United States Constitution. Complete and precise, yet open to interpretation and innovative application. It is a living document. You don’t just open it up for revision every time you encounter a new bump in the road. You let the umpires do their job. You’re undecided about instant replay.

And the ultimate measure of the sport’s health, as once noted by general manager Branch Rickey, is the number of fannies in the seats — or these days, the concessions and broadcast proceeds.

There has always been a friction in baseball — all sports in general, but baseball in particular — between owners, players and the fans, and the sports writers.

The friction is good. It’s the framework of competition. It’s a fundamental building block of capitalism — especially these days when most of the major leaguers are millionaires, just like their bosses.

So it’s not only our inner baseball purist dander that gets stirred up when we see changes come along, particularly in an economic climate that seems more driven by money than by principles.

Hmm. Last week, the Washington Post published an opinion column under the headline: “What do you call a sport in which half the participants aren’t trying to win? MLB.”

That’s disturbing if true.

This year we observe the 100th anniversary of the notorious Chicago Black Sox scandal, which involved players taking bribes from gamblers to intentionally lose the World Series.

Castro once called socialism “The gospel of envy.” No he didn’t. That was Churchill. Churchill apparently was too busy rebuilding capitalism in Europe in 1947 to develop his throwing arm. Thank the lord he stood on principles that are consistent with our own.