The comments add to the Barcelona news which been dominated by the club’s poor form this season.
Koeman’s side languish in eighth place in the league with just 17 points from their opening 11 rounds of matches and are nine points adrift from the summit.
The Dutchman was responding to criticism to his decision to bring on central defender Samuel Umtiti to replace Antoine Griezmann in the closing minutes for his side in Sunday’s 1-0 win over Levante.
He claimed that it was a move necessary to see out the victory and claim an important result before addressing the level of pressure and expectations at the Camp Nou.
Koeman told reporters at his pre-match press conference ahead of facing Real Sociedad, as per El Mundo Deportivo: “I understand the criticism when you lose four or five games, but I don’t understand the criticism for putting on a defender in the last five minutes when you need to win.
“At this club there is always pressure to win everything. You have to win everything, and people are used to that, but sometimes that is not possible.
“That is because there are changes in a team, and you have to accept that the team is not winning everything.”