D.C. United Coach Ben Olsen roared with anger after his team’s 2-1 loss to the Philadelphia Union in the U.S. Open Cup’s round of 16 Tuesday night.

Elimination from the 99th edition of the tournament before 3,276 at Maryland SoccerPlex was disappointing enough. The manner in which United performed prompted Olsen’s diatribe.

“We’ve been asking for this loss,” he said. “We’ve got to realize that’s not a good enough performance. Too many guys were on their own page. We were cute all over the field. We thought it was going to be enough to step out here and beat a team because they’re a little down on their luck.”

He wasn’t done.

“Maybe it’s a good thing because this really does show us we’re not as good as we think we are. All of the little things that got us success up to this point, we forgot about tonight. There were signs we were forgetting about that over the last couple games and we’ve been squeaking by. Tonight we didn’t squeak by.”

United is atop MLS’s Eastern Conference with an 8-3-4 record, while the Union is 2-7-2. On this cool evening, however, United was out of rhythm from the start and didn’t display the hunger and focus that had re-energized the organization.

Rookie Antoine Hoppenot scored less than two minutes into extra time for the Union, which will host a June 26 quarterfinal against the third-division Harrisburg City Islanders. The tournament involves teams from all levels of American soccer and sends the champion to international competition.

“It’s certainly eye-opening,” United forward Josh Wolff said. “It allows us to realize: ‘Look, we aren’t as good as we thought we were and there’s lots to work on.’ ”

The Union seized on a pair of fortuitous bounces in first-half added time. A deflection fell to Brian Carroll, whose shot caromed off Emiliano Dudar’s elbow and changed direction to slip behind committed goalkeeper Bill Hamid.

United answered before intermission. Andy Najar served a ball deep into left side of the box. Nick DeLeon headed across the six-yard box to Wolff for an easy nod into the right corner.

Neither side was able to gain attacking traction in a surly second half. United was fortunate to get to extra time after the Union faltered on multiple chances in the waning moments of regulation. A fully extended Hamid made a phenomenal save to stuff Hoppenot’s touch inside the six-yard box.

Philadelphia continued to find space in United’s back, and less than two minutes into the 30-minute extra session, Freddy Adu threaded a wonderful ball to Hoppenot behind Dudar for a clear run at Hamid and a composed finish.

United labored to respond, lacking the legs and ideas. Its leaky defending compounded the challenge. In the 105th, Hoppenot stabbed a 19-yarder off the crossbar.

Zac MacMath’s soaring save on Hamdi Salihi’s rocket preserved the lead. United’s Brandon McDonald and Philadelphia’s Carlos Valdes were red-carded for an incident in the 113th minute. Salihi’s misdirected volley in the last moments ended United’s hopes.

Said United’s Perry Kitchen: “Our last few games, we were kind of dying down and this can end up being a good thing for us because we have to realize we’re not where we want to be yet and if we don’t play well, we’re going to lose.”

The clubs will meet again June 16 in a regular season match at PPL Park in Chester, Pa.