Mets rightfielder Michael Conforto, center, speaks with manager Mickey Callaway,...

Mets rightfielder Michael Conforto, center, speaks with manager Mickey Callaway, left, and a member of the Mets staff after colliding with second baseman Robinson Cano as they failed to catch a fly ball that was hit by the Nationals' Howie Kendrick in the fifth inning on Thursday in Washington. Conforto left the game after the play.  Credit: AP/Patrick Semansky

WASHINGTON -- As Michael Conforto now enters the scary, and often unpredictable, realm of baseball’s concussion protocol, the Mets at least made sure to get him back to New York after Thursday’s 7-6 loss to the Nationals by the safest mode of transit possible.

On a train.

Those of us who were around the team during less conscientious times, back in 2008, remember when the Mets chose to fly Ryan Church from Atlanta to Denver after he was knocked cold at Turner Field. Fortunately, concussion awareness has come a long way since then, and the mistakes of the past can mostly be avoided.

But even with the meticulous attention paid to such brain injuries now, treating concussions is often like trying to navigate through uncharted waters. Each case may be different, becoming less or more debilitating, over an indefinite period of time, which is why it’s impossible to know right away the severity of Conforto’s concussion.

That’s the diabolical nature of this injury. In real time, the collision between Conforto and Robinson Cano, as both sprinted toward the foul line in pursuit of Howie Kendrick’s slicing fly ball, didn’t look that bad. At live speed, it appears that the Mets dodged a bullet. Cano isn’t able to make the catch, but he stays on his feet as Conforto goes down, which we thought at first was mostly due to the two briefly getting tangled up.

Slow the video down, however, and the damaging blow becomes clear. As Cano reaches with his glove hip-high, his usual basket-style, Conforto tries to go low, putting his head on a direct course with Cano’s left shoulder. Once Conforto’s face smashes flush into the shoulder, his body instantly goes limp as he falls flat on the grass. At that point, he appears to black out for a few moments, then struggles to get to his feet.

“I hit him really hard,” Cano said.

Obviously, Conforto wasn’t around postgame to tell his side of the story, but Mickey Callaway immediate feared the worst when he showed up with trainer Brian Chicklo. The two spoke with Conforto for a few minutes, then walked him off the field.

“He was kind of dazed when I got there,” Callaway said. “He was stumbling around.”

Just two innings before, it was Conforto who ultimately erased the Mets’ early 4-0 deficit by crushing a tying three-run homer off Nats’ reliever Erick Fedde in the third. It was a quick turn from that hope to the despair of Conforto’s status, uncertain other than him going on the seven-day concussion protocol at a time when the Mets can ill afford to lose one of their best run-producers.

That’s the immediate concern, from a baseball perspective. The Conforto-sized hole in the middle of the Mets’ too-inconsistent lineup. But a concussion is a larger, more amorphous threat, and rarely is solved by a week away from the game.

Travis d’Arnaud missed 16 days in 2014 after suffering his third concussion, the result of taking Alfonso Soriano’s backswing to the head, but still hit 13 homers with a .718 OPS in 108 games that season. That has to be considered one of the best-case scenarios.

Far worse is what happened to the Yankees’ Clint Frazier, a fellow outfielder, who crashed into the wall as he made a falling-down catch during a February spring-training game in 2018. Looking back, every concussion is treated seriously, but there is an optimism, too, because everyone expects headaches to clear.

Only with Frazier, the concussion-related symptoms wouldn’t go away, and what should have been a breakout season for him ended up broken. He played just 15 games in the majors, and couldn’t shake the physical tailspin until the following winter. It was a harrowing experience, and for a promising young player like Frazier, he wondered if his career would ever get back on track.

So mapping out just how long Conforto will need to return to the lineup, at this stage, is a pointless exercise. There is no answer for that. The Mets can only deal with his concussion on a day-to-day basis, while keeping their fingers crossed for a speedy and complete recovery.

“That’s sad news for the team, and all of us,” Cano said. “It’s the last thing you want to happen to your teammate.”

Cano is right about that. There is no surgery or medicine to solve the problem with this injury. The scope of a concussion’s damaging effects are so wide-ranging that you can’t do much more than hope for the best.

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