Deco concedes they've over-relied on Raphinha and Lamine Yamal this season and will seek to add a similar player to Hansi Flick's squad this summer.
He told ESPN: "Suddenly, we felt very dependent on Raphinha, on Lamine. Perhaps we need similar players, a solution for them. The squad is quite balanced, and we also have a lot of good qualities at the base.
"We have already renewed most of the contracts, now we have to take care of those who are there. Last year I said we couldn't lose anyone. I think it's the same now. If we can improve, it's always possible, but the key is to leave what we have consolidated for the coming years."
Best place for Yamal is here
Indeed, regarding Yamal's contract renewal, the Portuguese expressed his conviction that there will be no setbacks.
"The players have to be happy where they are. I don't see a better place for them. The kid grew up here; he's from here. This generation has the chance to make history.
"Putting myself in their shoes, I would want to be here, to be part of it. I don't see any problems, especially since he has a contract," Deco added.