Rashford is on-loan at Barca for the season with an option to buy for €30m.
Deco has also confirmed there'll be no penalty should Barca decide against signing Rashford permanently.
He told Sport: "No, it's a loan, and we have an option.
"I think it wasn't easy to come here. He has played at a very high level, with enormous demands at a club like Manchester United.
"Then he spent six months at Aston Villa, where he did a very good job. In fact, Aston Villa, they would have kept him if it had been possible. I know this because I've spoken to people there. But he only wanted to come to Barca, and that's a very positive thing.
"We were able to secure a loan. The fact that he took a pay cut to make it happen is a clear demonstration that he really wanted to come, and we're very happy about that.
"He's a player who contributes a lot to the team."