Under new coach Hansi Flick, Barca sit top of the table with a 100 per cent record.
Deco said of the German, "He is a calm man, a football person, a hard worker. He is a coach with clear ideas, very demanding, very clear about what a football player has to do and what people have to do on a day-to-day basis.
"The idea was that if the young players were working, we wouldn't have to go to the market so much. We had to find the balance and know what was missing and I think we found it. The signing of (Dani) Olmo gives us balance in the midfield, he has a different profile, we gain in offensive quality.
"There were offers for several of our players, but we were clear that we didn't want to lose important players. If we're building a team, we can't undo it. We have to raise the level, not lower it, and selling an important player means lowering it.
"We couldn't fall into the temptation of selling, but it wasn't easy. Not selling is very complicated because you can't buy. But I was very clear that the important thing was not to sell the important players and to know what we had at home. The bet must always be on the club."