Perry Kitchen of D.C. United dribbles against Philadelphia. United won the game on a goal by Chris Pontius in the 78th minute. (Hunter Martin/GETTY IMAGES)

D.C. United forward Chris Pontius had just touched in a perfectly served free kick from midfielder Branko Boskovic at the far post, but in the immediate moments after the ball hit the back of the net, Pontius was not sure what had happened. “I was so confused because he blew the whistle so fast and their guys started taking off,” Pontius said. “So I was thinking maybe he called a foul on us in the box.”

In fact, the 78th minute goal was good, and United held on for a crucial 1-0 win over the Philadelphia Union on Saturday night at PPL Park to remain atop MLS’s Eastern Conference.

But the hesitation felt somewhat appropriate because the goal was a bit surprising.

D.C. had spent much of the match absorbing pressure against an energetic Union team playing its first game under a new coach. Only on a few occasions had United appeared a threat to score.

Yet this D.C. team continues to show it has the weapons to take advantage of any slim chance. And the gritty result was as valuable as any lopsided score line, United Coach Ben Olsen said.

“That’s what you have to do in away games in this league,” Olsen said. “It’s not easy. You come to these places, they’re at home, they’re buzzing and you have to get results like this throughout the season. I’m proud of the guys tonight.”

John Hackworth, the interim coach named to replace Peter Nowak, who was fired on Wednesday, received a loud ovation when introduced before the game. And Philadelphia’s lineup reflected his influence – namely the insertion of Jack McInerney, the 19-year-old forward who had played just 93 total minutes this season.

While D.C. lacked verve going forward in its first league game in three weeks, Philadelphia (2-8-2, eight points) – perhaps motivated by the coaching change – shook off early rust and put constant pressure on United’s back line.

Goalkeeper Bill Hamid fumbled a lasered Freddy Adu shot in the 12th minute and McInerney nearly touched a 16th minute free kick past the sprawling Hamid. United also needed a big save from Hamid in the 22nd minute when he denied Josue Martinez on a through ball from Adu.

United was better in the second half at containing Philadelphia’s roaming midfielders and forward line.

In the 77th, Pontius was sent flying by a tackle from Carlos Valdes. The replay appeared to show that Valdes got the ball first, then made late contact with Pontius. The home fans thought it was a clear-cut dive.

Boskovic served a curling ball that narrowly missed two United players before Pontius hit it in-stride at the far post for the win.

“We didn’t play particularly well tonight,” Pontius said. “I thought they had most of the possession, the better of the game. . . . In these games, it’s about finding a way to win. We were able to do that tonight.”

SPORTING KANSAS CITY 2, TORONTO FC 0: C.J. Sapong and Julio Cesar scored in the first half as host Kansas City spoiled the debut of new Toronto Coach Paul Mariner.

CREW 0, REVOLUTION 0: Andy Gruenebaum made five saves for his fifth shutout of the season to lead the visiting Crew in a scoreless draw.

●●IMPACT 4, SOUNDERS 1: Felipe Martin, Justin Mapp, Andrew Wenger and Lamar Neagle all scored to help host Montreal defeat Seattle.

WHITECAPS 1, RAPIDS 0: Sebastien Le Toux’s goal in the 80th minute gave undermanned Vancouver a big win at home.

DYNAMO 2, FC DALLAS 1: Adam Moffat scored his first goal of the season in the 76th minute as Houston won at home.