WASHINGTON – Patrick Mullins went the full 90 without a shot on goal for just the second time this season.

Luciano Acosta got so agitated that teammate Bobby Boswell forcibly shoved him to keep him off referee Jair Marrufo.

And Lloyd Sam lasted only 60 minutes before D.C. United head coach Ben Olsen turned to Lamar Neagle for reinforcements off the bench.

For the trio of attackers that had fueled United’s offensive rejuvenation in the second half of 2016, Thursday’s 4-2 Eastern Conference Knockout Round loss to the Montreal Impact was a cruel end.

“We never really got going,” said Mullins, who had scored eight goals and added two assists since joining D.C. via trade from New York City FC in July. “We liked our chances, we liked how our form was going. … But that has nothing to do with the game once it starts. And we had to perform. And unfortunately we didn’t put out our best performance.”

Mullins, Acosta and Sam had spearheaded an attack that scored an outlandish 34 goals in its last 14 matches. But neither Mullins or Acosta had started a playoff match before. And their task became even tougher than your average win-or-go-home encounter when a skillful counterattacking Montreal side got a coveted early goal.

“They sit in a lot and don’t really press you so you can’t break them down easily,” said D.C. defender Steve Birnbaum. “So credit to them, they had a good game plan, and they executed well.”

When the trio did show glimpses, they were rarely connecting with each other.

Mullins was nearly freed on a breakaway early by Nick DeLeon’s deflected pass. Sam’s most tempting cross almost found Patrick Nyarko for a clear header.

As for Acosta, his best moment may have come when he rounded one defender near the byline, only to tumble inside the 18 under Marco Donadel’s questionable challenge.

Marrufo let play continue, setting off the Argentine’s furious reaction.

“I think they were extremely physical on Lucho, Patrick Nyarko, Lloyd Sam,” D.C. coach Ben Olsen said. “They’re a physical team, and overall I thought they were very good front to back. The early goal again helps them. And allows them to keep their shape and stick to what they’re good at.”

Acosta lasted only five minutes more than Sam before giving way to Julian Buscher. As the 22-year-old walked off the pitch, he gave a one-armed wave to the RFK Stadium supporters, leaving some to wonder what his future might hold when his loan from Boca Juniors expires this offseason.

Afterward, Olsen insisted it was just a frustrating night, and not a sign for the future.

“That’s what most [22]-year-olds have to go through,” he said. “Yeah. We certainly want him back and think he’s going to be a vital piece to this organization for the next couple years. He’s a lot of fun to watch, he’s a lot of fun to coach. And he’s a great kid. I’m looking forward to working with him next year.”