Brace yourself, baseball fans, and behold the inexorable rise of the bat flip.

Self-expression has long been a fraught issue in Major League Baseball, where impassivity — the ability to “act like you have been there before” — often feels as highly regarded as power hitting and foot speed.

Yet times change, and signs today indicate that baseball stands poised to enter a golden age of celebratory antics. If so, bat flip buffs might one day look back upon this week’s playoff games as a symbolic starting point.

It began last Monday. Upon pulverizing a three-run homer into the upper deck at Citi Field, Yoenis Cespedes of the New York Mets cradled his bat for a moment before flinging it skyward in celebration, like a bride blissfully tossing a bouquet. The crowd went berserk.

But that majestic flip was reduced to a quaint memory two nights later, when Jose Bautista of the Toronto Blue Jays performed what might have been the most ostentatious bat flip in MLB history. The moment came after Bautista smashed a late tiebreaking home run at Rogers Centre. Bautista watched the ball’s flight, glared into the near distance like a professional wrestler and then, in a burst of pugnacious swagger, hurled his bat deep into foul territory.

Anyone could have predicted how the Texas Rangers, who lost the game and the American League division series, would react.

“He’s a huge role model for the younger generation that is coming up playing this game, and he’s doing stuff kids do in whiffle ball games and backyard baseball,” said Rangers reliever Sam Dyson, who helped incite the benches to clear when he voiced his objections on the field. “It shouldn’t be done.”

But Dyson’s response came in sharp contrast to those of fans on social media, who celebrated Bautista’s move with a torrent of Twitter posts, GIFs and Vine videos. The MLB account on Twitter posted videos of Cespedes and Bautista side by side and asked, “Who flipped it better?”

For bat flip aficionados, the speed, trajectory and distance of a toss are crucial details. Midair rotations add to the visual splendor. Dramatic posturing and histrionic facial expressions elevate things to the next level. Bautista’s flip had it all.

Until now, the subject of bat flips has generally left little room for a middle ground. People love them or hate them — there is an unmistakable generational divide — and they feel compelled to air their stances either way.

To some, the maneuver symbolizes a break from the gentlemanly principles that have supposedly steered the game across generations.

“You play so many games and fail so many times, so the game has a way of humbling you,” said Kelly Johnson, 33, a Mets utility player, who guessed that players mostly objected when a young or unaccomplished player behaved arrogantly. “That’s the message veteran players sometimes try to pass on to rookies, that their actions should try to reflect that.”

To others, the bat flip represents a breath of fresh air in a stuffy sport and reflects the game’s increasingly diverse clubhouses, which feature more players from Latin America and Asia, where such celebrations tend to be more common.

“In my opinion, after being in Asia and the United States and also seeing Latin American players for so many years, it seems like Americans need to lighten up,” said Ryan Sadowski, a former major leaguer who works as a scout for the Lotte Giants of South Korea. “The fans clearly enjoy it.”

The debate will continue, but bat flips are unambiguously on the upswing. Some players are lightening up. Others are merely acquiescing.

Inside the New York Yankees clubhouse before a late summer-regular season game, catcher Brian McCann let out a small sigh when asked for his position on celebratory bat flips.

McCann has developed a reputation as one of the vigilante enforcers of baseball’s traditional code. With the Atlanta Braves, he confronted players and caused fights on multiple occasions for what he perceived to be unseemly behavior after home runs. But, McCann said, sports evolve, and people change.

“It’s where the game is going, where the game is at, really,” he said. “It’s what guys are doing.”

McCann joked about hearing stories of days long past, when a batter might get a ball thrown at his head for simply swinging too hard. These days, he said, umpires are quick to issue warnings and ejections for even a vague hint of belligerence. That reduces the informal, internal policing among players — no one wants to be thrown out of a game — and opens the door for more flamboyant behavior.

McCann said he still objected when batters made things personal or overly confrontational.

“I’ll stick up for my pitcher every time,” he said. “I get fired up just like anybody else, if not more than most people, and do what comes natural.”

To the delight of some fans, more batters are feeling comfortable doing what comes natural.

Late Wednesday night, after the game, Bautista was told that Dyson had called the bat flip celebration childish. Bautista was asked if he had any response to such criticism. He shrugged.

“No,” he said. And many others felt the same way.