Clint Frazier said it was like being in “a state of euphoria,” though that barely describes what really happened to the Yankees outfielder last summer. A chronic concussion, which lingered for months, not only robbed Frazier of a year of his career but left him with black holes in his memory — entire swaths of 2018 he can’t recall.

“I felt like I wasn’t physically there, like something I couldn’t get out of. I was scared,” he said by telephone on Tuesday. “There were times I’d be driving, like I was on auto-pilot or something. I’d look around and think, ‘How did I get here?’ ”

Finally, after an endless battery of tests and medical work-ups, Frazier has been cleared to return to the Yankees. He’ll be in Tampa in a few weeks, looking to win the left-field job — which appears wide open. Frazier promises all the assets that made him attractive to the Bombers are still intact, including the bat speed general manager Brian Cashman once called “legendary.”

It’ll be an inspiring comeback if Frazier can indeed beat out Brett Gardner. Frazier has been training at a sports-performance facility in suburban Atlanta, so locked in not even a pitching machine set to 103 mph — from just 52 feet away — seemed to be a problem.

Frazier’s real demons, though, have been harder to calibrate. There’s no diagnostic tool to measure a concussion’s severity, other than a patient’s own description of the symptoms. And there’s no medicine a doctor can prescribe other than rest and patience. A pitcher recovering from Tommy John surgery has a pretty good idea how long it’ll take to get back on the mound. Not so with a head injury.

Frazier soon realized trying to find a cure was like trying to catch dollar bills dropped from a skyscraper. He grasped for a breakthrough which never came, continuing to suffer with symptoms while the season slipped away.

“We all play sports for the memories, right?” Frazier asked. “But what if you can’t remember them?”

Frazier offered a second, salient thought about life with a concussion.

“You ever been on a treadmill, going really fast, and then suddenly hop off?” Frazier asks. “There’s that brief moment when you don’t really feel your feet. That’s what I felt like all the time.”

The downward journey began in late February, when Frazier crashed into a wall during a spring training game. He got to his feet but realized something was “off” — like a “hangover times 10.”

Doctors diagnosed Frazier with a vestibular concussion — a nasty cocktail of blurry vision, headaches, nausea and dizziness that could be triggered not only by light or sudden movement, but by emotions as well. That left Frazier vulnerable to just about everything.

“Every time I got mad or upset, I’d feel this change in my body,” he said. “That was the hard part, trying to live a normal life. But I was walking on eggshells all the time.”

Sleep was no refuge, either. If Frazier slept too little, he said, “I felt terrible.”

Too much sleep? “It was just as bad.”

The breakthrough he and the Yankees hoped for never happened, at least not for any extended period. Frazier was limited to just 54 at-bats, including an attempted rehab stint in the minors. What should’ve been a prime opportunity to shine — Aaron Judge’s seven-week stay on the disabled list with a broken wrist — was instead a final verdict on Frazier’s lost season.

He simply wasn’t ready, forcing Cashman to trade for Andrew McCutchen. Yet the front office never lost faith in Frazier. McCutchen, a free agent this winter, was allowed to walk, ultimately signing a three-year deal with the Phillies.

In the meantime, Frazier has been in steady contact with Cashman, who promises the Yankees still have faith in the outfielder’s skills and that a spot is waiting for him on the 2019 roster. That loyalty is one reason why the Yankees have apparently passed on Bryce Harper, though their outfield is already overcrowded.

Nevertheless, with six players vying for three positions, the Yankees’ goodwill toward Frazier is finite: He’ll have to earn the job, and more importantly, prove he can hold it by staying off the DL. To this, Frazier says: Bring it.

He was green-lighted two weeks ago by Dr. Michael Collins, who’d been treating Frazier out of the University of Pittsburgh Medical Center. Frazier was spun around, twisted, turned and literally hoisted upside down to see if his symptoms returned. They didn’t.

Collins told Frazier he was fully in the clear, with no chance of a relapse barring another head-first collision into a wall. Still, there are rules to follow: no sleeping past 9:30 a.m. ever, no alcohol, and regular exposure to loud noises — yes, very loud noises — to prepare the slugger for the decibels of sound awaiting at the Stadium.

Frazier has taken the advice literally, attending concerts all winter — Drake, Elton John, Travis Scott, Migos — sitting as close as possible to the stage. And to further ramp up, Frazier has acquired a new nickname, “The WILDLING,” straight out of “Game of Thrones.”

“That’s going to be me, I’m going to be Wild Thing,” he said. “Wearing eye black, got my nose pierced, wearing No. 77, crazy hair.”

He laughed, then exhaled for what felt like the first time in forever.

“I want the Yankees to know I’m going to be the same player they’ve gotten glimpses of,” Frazier said. “I can’t wait to get to spring training because I’m ready, I feel great. This is going to be a big year for me.”

All set to make memories — this time, unforgettable ones.