The former Barcelona star says Leeds chief Victor Orta was the key in the deal.
"When I spoke with the club, one week to the close of the transfer window, they say to me they maybe could think about this move for Raphinha.
"I start to work I spoke with Leeds, because I know Victor Orta likes him very well and Victor call me and say, 'okay maybe it's possible or not, we'll see'. It was fast, but like I say in football, sometimes there are [these] kind of opportunities."
Deco explains that Orta and the club's hierarchy's clear desire for the player was a big part of Raphinha's decision to sign.
"In football sometimes, it's important when someone wants you - really wants you - and Leeds they showed how much they want Raphinha.
"That's why it was important for him. He was happy, he saw the people when they call, Victor [Orta] and the President they call him and want him and this is important for the player too.
"That's why they convinced Raphinha to come."