The Catalans dropped points again at home to Granada on Monday night, failing to get over their Champions League loss to Bayern Munich last time out.
"Look at our squad list," Koeman said after the game, when quizzed about Barcelona's setup and style.
"We did what we could. We don't have the players from the tiki-taka days. We have to play with our own style.
"I think we did well and, with some more time, we could have won. The basic system was 4-3-3 in the first half, then I had to make changes based on what I had on the bench.
"This isn't the Barcelona of eight years ago. That's the way it is.
"With Ansu [Fati] and [Ousmane] Dembele it's different because we have more depth."
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