"To be fair about Deco, I feel it's very difficult for a Chelsea player to come to me," the Portuguese told a news conference ahead of Saturday's Italian Super Cup against Lazio at the Olympic Bird's Nest stadium.
"Every time I'm interested in one of their players, it looks quite different. In the summer we were told he was almost free to come. Two weeks later, when they know Inter are interested, it goes zero to five (million) and for Carvalho from five to 15 (million). Something like that."
Deco and Carvalho were both part of the Porto team Mourinho guided to Champions League victory in 2004.
Carvalho was one of Mourinho's first signings following his subsequent move to Chelsea, while Deco joined the London club in 2008 after a successful spell at Barcelona.
Mourinho, who has brought in four new players since the end of last season, said he would still like to add a playmaker to his side, even if it was not Deco.
"We want a playmaker, yes," he added. "It's a position for a long time we think we needed. (Dejan) Stankovic did a great job for us last season (but) it's not his best position for the team.
"We are looking for a player. Who? I don't know. I'm more about the structure, I leave names for the club structure."
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