He’s a firefighter in name only.

Michael D. Johnson won’t fight fires. Instead, he stays on the sidelines as his Engine Company 257 colleagues rush into burning buildings, FDNY insiders told The Post.

Nicknamed “Tragic Johnson” by the rank and file, he’s managed to evade the smoke and flames several times since joining the Canarsie, Brooklyn, firehouse last year, sources confirmed.

“To have a guy that you know to be afraid is not going to be there for you when you need him to be — it’s frightening,” said one FDNY source.

The latest fright unfolded April 2 at a three-alarm blaze on East 78th Street, when Johnson’s irked captain radioed a “mayday” after discovering Johnson was AWOL, sources said. He had been assigned as “backup” to the nozzle man carrying the hose into the burning two-story building.

That left just two firefighters — the first and a third — to haul the heavy hose up a long staircase and spray water on the flames.

A photo obtained by The Post shows Johnson at the curb next to an FDNY vehicle while fellow firefighters march up steps into a house engulfed in black smoke.

Johnson told his colleagues that he’d returned to the fire truck to refill his air tank, a source said.

But sources said he never entered the blaze and should not have run low on air.

“It can’t be ignored,” another department source said of the probie firefighter’s repeated absences. “If they ignore it, some civilian will end up injured or killed, or a fireman will be injured or killed.”

“Everyone is concerned about working with him,” said a third source. “We’re concerned for our safety, but we’re also concerned for his safety.”

But department members are afraid to openly complain or criticize Johnson, who is black, because he was hired under a court order to increase minority hiring in the FDNY.

Johnson, 41, a former city EMT who earned two medals on that job, was among 282 “priority hires” — applicants passed over in 1999 or 2000 as a result of discrimination, a federal judge ruled.

His June 2, 2014, graduation class of 286 probationary firefighters was hailed as the most diverse in FDNY history — 24 percent Hispanic, 17 percent black and with four women.

While most priority hires — including others at Engine 257 — have become outstanding firefighters, sources said, Johnson has fumbled. It took him three attempts to pass the Fire Academy, they said, and he has been sent back for retraining twice. “He’s a nice enough person, but he’s certainly lacking in the ability to put himself in harm’s way,” one source said.

The fire boss who radioed the “mayday” — a rare code used only to signal that a firefighter is lost in a blaze or in distress — knew Johnson had stayed outside but wanted to document his absence on the recorded transmissions, sources said.

Shortly after the incident, a chief sent a letter to the Brooklyn division describing concerns about Johnson, a source said.

The department confirmed Saturday that the April 2 mayday resulted in an official department order to retrain Johnson.

After his weeklong retraining, a source said, Johnson indicated he didn’t want to return to the Canarsie firehouse but was ordered by department brass to do so.

“The department seems to not want to give a f–k about any of this because they want to fill their quota,” the source added.

Reached at his home on Saturday, Johnson refused to answer questions about his performance or address the complaints, saying he was not authorized by the FDNY to speak.

“To have a guy that you now have to be afraid is not going to be there for you when you need him to be — it’s frightening.” - FDNY source

Of the mayday, he said only, “The captain never said anything to me. I have to go to my station and ask them what they’re talking about. So many things could be said and not be true.”

Johnson saw his salary soar from the $44,520 he made as an EMT in 2008 to $76,488 last year as a firefighter, according to See Through New York data.

Johnson would not address reports he took several days of medical leave for stress following the April 2 fire and several months’ medical leave after a fire in a six-story apartment building on Rockaway Parkway last July 4th weekend.

Insiders insisted they were not targeting Johnson because he was a “priority hire,” noting the Canarsie firehouse has black and Latino members and a female firefighter who are all highly regarded.

But Johnson’s advanced age as a rookie may have made it more difficult for him, sources said.

“He’s now in the position where he has to do a job that’s not meant for a 40-year-old to start,” one said. “He’s slow and he’s a danger.”

FDNY spokesman Jim Long would not discuss Johnson’s performance or record, but said, “Probationary firefighters receiving additional training, or going back for retraining, is a normal practice in the department.”

Officials noted that Johnson and other Fire Academy graduates remain under probation — and evaluation — for a year after they enter the field.

Those who do not successfully complete probation can be fired, officials said. Johnson will mark his first year as an FDNY firefighter in two weeks.