Christophe Galtier was enraged by Paris Saint-Germain's "catastrophic" start after the Ligue 1 leaders were hampered by injury and illness in a 3-1 defeat at Monaco.
Hamstring issues had already left PSG without Lionel Messi and Kylian Mbappe at the Stade Louis II, while Fabian Ruiz was surprisingly absent and Achraf Hakimi and Sergio Ramos began on the bench.
PSG were torn apart in the first half as Wissam Ben Yedder scored twice after Aleksandr Golovin's opener, capitalising on an error from 17-year-old defender El Chadaille Bitshiabu for his first.
The visitors were unable to build on Warren Zaire-Emery's response and have now suffered three defeats in their last seven league games, as many as in their previous 45.
While selection issues plagued PSG on their trip to the principality, Galtier viewed their slow start as unacceptable.
"I am furious because the start is catastrophic," he told Amazon Prime Video. "We had hope with the goal, and we concede a third on a transition. Going back to 3-1 is more complicated.
"There is anger. There were absentees, a virus. It's a difficult time for everyone, the players and the fans.
"We have a big meeting on Tuesday [against Bayern Munich] and we need to regain energy, confidence and available players. We've conceded a lot of goals since the restart. We have to find balance.
"In the second half, there were zero shots and no reaction. It is insufficient. After three minutes, the plan fell through."
PSG's tally of three league defeats in 2023 is their most after seven games at the start of a calendar year since their 2011 takeover by Qatar Sports Investments, last enduring a worse start when they lost five of their first seven Ligue 1 matches in 2010.
Having exited the Coupe de France against Marseille in midweek, PSG face a huge Champions League last-16 meeting with Bayern Munich on Tuesday, and captain Marquinhos knows the importance of responding to Saturday's setback.
"After a disappointment, we know that we have to bounce back quickly," he said. "We have to talk to each other, let everyone look at each other to see what they can do better.
"You must not let go. We lost the cup, we have the Champions League, we are first in the championship... why would we give up now?
"We are going through a difficult moment, but we have to go hard; it's a key moment of the season."
