The 17 year-old has agreed a new deal to 2031 with the Catalans.
Asked about comparisons with Lionel Messi, Deco told BBC Sport: "Lamine is Lamine. Leo is Leo. Leo was the best player in the history of this club, for me, the best player in history.
"Everyone becomes crazy when they see Lamine playing football, you would pay to go watch him in the stadium, he's special and he wanted to stay because he believes in the project. He deserves an improved salary.
"He's going to be one of the best players in the world. We need to respect him as a player, but not forget he is 17 years old."
Deco added: "It's not easy to compare, but Lamine, in terms of quality, can make history like Leo. But of course, to make history, he needs to have a good team behind him."
Everyone wants Lamine
Deco admits they're having to manage Yamal's commercial commitments, conceding the frenzy around the teen is only increasing,
"We try to not let him do everything, because, you know, sometimes the sponsors, and everyone wants his shirt or time," Deco continued. "Sometimes we can't control everything, but people see his magic, on and off the pitch.
"They want to have a piece of him and we need to help him manage that."