Claude Puel said Southampton were punished for going away from their philosophy in the first half at Crystal Palace.
Saints fell to a 3-0 defeat at Selhurst Park, as Christian Benteke struck twice, either side of a James Tomkins goal.
Puel was unhappy with the way his team had approached the opening 45 minutes, when they conceded twice, and admitted that they had then given themselves too much to do.
"It's disappointment, but congratulations to Crystal Palace – they made the maximum of our mistakes today," he said.
"In the first half, we didn't have enough play on the ground and for us it was a bad first half, without chances, without the ball, with duels and long balls, and this is not our game.
"It's important to stay with our philosophy against any opponent and it was difficult against this team.
"The first and the second goal permitted them to stay behind the ball and it was always difficult to find solutions with a bad pitch and the opponent's strong defence.
"The first half was not sufficient for us. We tried to play in the second half, with chances, but it was a bad game for us.
"After the second goal we tried in the second half to have better intentions, but it was difficult to come back."