Frank de Boer was frustrated Crystal Palace did not "show some balls" until they were 2-0 down to Swansea City on Saturday.
Palace are without a point or a goal in the opening three games of the Premier League season, with De Boer enduring a tough start to life with the Eagles.
Goals from Tammy Abraham and Jordan Ayew punished Palace mistakes at Selhurst Park and only then did the hosts kick on, much to their manager's dismay.
"We have to show some balls from the first second of the game," De Boer told BBC Sport. "It wasn't until after we were 2-0 down that we showed we really can play.
"It was not because of the quality of Swansea that we lost. We made two mistakes, they had two half-chances and scored both times.
"It is a very hard lesson for us. If we do not show balls or courage then you get punished.
"In the second half, you saw a different Palace, who creates chances and with a bit of luck you score one of those. It just wasn't the day for us."
Although Swansea also had not scored in the league prior to this victory, manager Paul Clement now believes his side can consider this a good start to the season.
"We played two games away from home and won four points, our home game was against Manchester United," he said.
"To also go through in the EFL Cup, we can say it has been a decent start to the season."
On potential transfer business, Clement added: "We have our eye on a couple of transfer targets.
"We will try to bring in some quality players to be competitive this year."