An embattled NYPD detective faces the loss of 25 vacation days and a year on departmental probation for misconduct that included challenging a fellow cop to fight him at a police boxing exhibition, the detective’s lawyer said Wednesday.

An administrative judge recommended the penalty against Det. David Terrell in a ruling that found him guilty of five departmental charges and partially guilty of two others, following a trial last month.

Terrell’s punishment will be decided by Police Commissioner James O’Neill.

The NYPD said there was no timetable for when O’Neill will hand it down.

Terrell’s lawyer, Eric Sanders, called the sanction suggested by NYPD Assistant Deputy Commissioner Paul Gamble “outlandish,” and claimed that Terrell was being targeted over a sweeping, federal civil-rights suit he filed in April against the city and a host of other defendants, including O’Neill and de Blasio.

“They’re going after him because they don’t like that he’s challenging their system,” Sanders said.

Terrell’s legal action followed a series of unrelated misconduct suits filed against him in recent years, three of which were dismissed earlier this month.

He claims the city is too quick to settle suits against cops, and paid out $614,500 over allegations in a 2013 case involving him and 10 other cops “without consulting him” first.

Terrell, 45, has been stripped of his badge and gun since a series of incidents that include a May 2, 2016, confrontation with highway cop Christopher Rivera after Rivera stopped Terrell, who was off-duty and headed to work at the 42nd Precinct in The Bronx.

During a recorded conversation, Terrell called Rivera a “jerk” and told him: “I’m inviting you to a smoker, we can handle it there.”

A “smoker” is police slang for a series of boxing matches where cops battle each other, sometimes to settle grudges.

Terrell was also charged with failing to tell the NYPD about a May 13, 2016, order of protection obtained against him by his since-divorced wife, and of failing to have his NYPD-issued, 9-mm pistol fully loaded when he surrendered it on June 1, 2016.

Terrell said his recommended punishment “really is excessive.”

“I’m just hoping that the police commissioner looks at all the evidence and comes to a good decision,” Terrell said.

“I committed no crime, I didn’t get arrested, I didn’t do anything criminal. I just invited [Rivera] to a smoker and if you go on YouTube, cops do it all the time.”

Terrell, who’s racked up more than 1,000 arrests since joining the NYPD in 2002, also noted bitterly: “I’m one of the hardest working officers on this job, and this is the reward for working hard.”

Additional reporting by Stephanie Pagones