Lititz, Pa., native Andrew Wenger slammed a header past Zac MacMath in the 44th minute, and Brazilian midfielder Felipe hit a spectacular sideways volley in the 78th minute to deal the Union a 2-0 loss.
"As a team, we did a lot of things well tonight, [but] we didn't execute in front of goal," Hackworth lamented after the game. "That's the most important part of the game."
Indeed, the Union (7-11-2, 23 points) had a fair number of good looks on goal. The first came in the 21st minute, when Lionard Pajoy hit the post with a shot after sprinting through a Montreal (9-13-3, 30 points) defense anchored by Italian legend Alessandro Nesta.
Seven minutes later, a close-range header from Jack McInerney forced a diving save by Impact goalkeeper Donovan Ricketts. And in the 83d minute, Ricketts just barely palmed a loose ball out of his six-yard box before Carlos Valdes could poke it home.
But the night's biggest talking point came far from either net, near midfield.
In the 69th minute, Impact defender Nelson Rivas and Union forward Antoine Hoppenot got tangled up and hit the turf. After both got up, Rivas head-butted Hoppenot in plain sight of the referee - not to mention the 18,535 fans in attendance, including a sizable contingent of traveling Union supporters.
With Hoppenot still on the turf, McInerney came up behind Rivas and shoved him. Referee Ismail Elfath immediately ejected both players from the game.
Hackworth vehemently disagreed with Elfath's decision to dismiss McInerney, even though the retaliatory nature of the shove was clear.
"It's unbelievable that we were not up a man for the last 22-plus minutes," Hackworth said. "You cannot tell me that a head butt to the nose and cheekbone, and a player going to push another player, [are] justifiable for equal punishment."
Freddy Adu - who, despite being 23 years old, is one of the Union's most experienced players - relayed to reporters the conversation he had with Elfath after the incident.
"He said that Jack tied his hands by pushing the guy down to the ground," Adu said. "At the end of the day, we've got to do a better job of keeping our heads."
The ejections ended up overshadowing the fact that the Union's struggles away from PPL Park continue. Their opportunities to claim a road win are dwindling. So too may be their slim hopes of making the MLS playoffs.