It was a result that sent shockwaves through Major League Soccer and embarrassment to the defending MLS Cup champions.

And after Atlanta United’s stunning 5-1 road defeat to the Chicago Fire, manager Frank De Boer wasn’t sugarcoating his disappointment.

"It's not explainable I think," De Boer said to media postgame. "Every aspect of the game we weren't there. We weren't ready. I have to blame myself first because I have to prepare them. But we have to be ashamed for the 45 minutes for our fans who came here ... We were really embarrassing today, especially the first half.”

That first-half went pear-shaped early with Leandro Gonzalez-Pirez sent off on a straight red card in the 11th minute for DOGSO. By that point, Atlanta already dug itself a two-goal hole and Nico Gaitan’s subsequent penalty kick gave the Fire a commanding lead.

CJ Sapong and Fabian Herbers scored seven minutes apart late in the first half to send Chicago into the break with a five-goal advantage.

"The game was over in 10 minutes," goalkeeper Brad Guzan said. "There was no rhythm.”

Brandon Vazquez converted from the penalty spot in the 58th minute for the lone goal of the second half, but that was little solace to De Boer, whose side suffered its most lopsided defeat in the club’s short history.

"We won the second half 1-0, but you saw the energy you want to see," De Boer said. "But it was too late.”

De Boer hopes the defeat provides the necessary wake-up call for a team that has seen its form drop of late. Of particular concern for Guzan is the nine goals conceded in the last three games, two of which were defeats.

"We need to have honest conversations and a real look in the mirror as a group because the last couple of games certainly hasn't been good enough defensively," Guzan said. 

Before moving on to a showdown with the New York Red Bulls Sunday (2 pm ET | FOX, MLS LIVE on DAZN in Canada), De Boer told his team to remember how Wednesday’s defeat felt.

"Understand that you don't want to feel that feeling again' — the embarrassment, the shame that you feel,” he told them in the locker room.

As for the lookahead to Sunday, De Boer assured reinforcements, at least in the attacking third, are coming with star striker Josef Martinez integrating back with the team after competing with Venezuela at Copa America in Brazil.

"Josef [Martinez] was mentally and physically still not prepared," De Boer said. "He's very important for us and he will be there [against] Red Bulls. That's for sure."