CHESTER, Pa. — In the 74th minute of an MLS match Saturday at Talen Energy Stadium, referee Sorin Stoica issued a red card to D.C. United’s Luciano Acosta. The Argentine playmaker had challenged Philadelphia’s Haris Medunjanin from behind along the sideline near midfield. It was worthy of a foul, maybe a caution, but certainly not an ejection.

Acosta was dumbfounded. His teammates were incredulous. But perhaps no one was more surprised than Medunjanin.

So the Union midfielder approached Stoica and told him he didn’t think it was a red-card offense.

Yes, an opposing player asked the referee to reconsider punishing the other team’s most important attacking player.

Persuaded by Medunjanin’s honesty, Stoica allowed Acosta to remain in the match.

“I think you need to be honest,” Medunjanin said afterward.

Through a pool reporter, Stoica confirmed he had spoken to the Philadelphia player before changing his mind.

Medunjanin, a member of Bosnia’s 2014 World Cup squad who is in his first season with the Union, described what happened:

“I was protecting the ball, and suddenly [Acosta] pushed me in the back. And then I saw the red card. I spoke a little bit to Acosta, and he was saying he didn’t kick me. I said I didn’t feel it also. I went to the referee and he said, ‘Did he kick you?’ I said, ‘I don’t think so. I think it was just a push.’ That’s why it’s no red card, for me.”

After the confusion, the natural assumption was that the assistant referee had persuaded Stoica to rescind the card. But after the match, United Coach Ben Olsen revealed that it was Medunjanin who had persuaded Stoica.

“I’ve got a lot of respect for that,” Olsen said. “He’s a classy player and a pretty classy human being.”

Olsen approached Medunjanin, 32, after the final whistle and thanked him for his sportsmanship.

“I said, ‘No problem.’ This is football. We fight for the three points, but we need to be honest,” Medunjanin said. “I’m always honest. I try to win. I don’t want to win with a dirty play. For me, it’s important that we won and play a fair game.”

Union Coach Jim Curtin said he agreed that Acosta did not deserve a red card but added with a laugh, “I don’t know if I would have done” what Medunjanin did.

Curtin expressed admiration for his player, saying, “You talk about fair play in this league and all over the world, he’s the one who had the intestinal fortitude to speak up and say there was no contact. He’s a man. He’s a person I respect a great deal. It’s an incredible act. I think it’s something you could show to not just young kids but adults who play in professional soccer. What he did is very honorable, the right thing to do. … But he did what is right for the game.”

When Stoica showed the red card, United captain Steve Birnbaum approached the referee to dispute the decision. “He told me he saw something,” Birnbaum said. “He thought he made the right call until their player said something to him. That was pretty big of [Medunjanin]. I don’t know if I would’ve done that.”

Although Medunjanin’s input helped United remain at even strength, the Union staved off late pressure to secure a 1-0 victory and end a three-game losing streak.

“I can talk now about being honest because we won the three points,” he said. “It’s much easier to speak [about it], but maybe if it’s a draw, maybe it’s a little bit different.”