Quaresma joined the Blues in a loan deal from Inter Milan on transfer deadline day.
Deco said: “Quaresma is young but has improved a great deal in recent times.
“He can be a very good reinforcement for Chelsea with many decisive moments in the season coming up.
“The Premier League may suit Quaresma more than in Italy. I believe he can have more success here.
“I am surprised it did not work out for him at Inter, especially as it was Jose Mourinho who wanted to sign him last summer.
“He is a player with fight, determination, swiftness and great vision on the field.
“He can make things happen and unlock opposition defences.
“On the ball he is a fantastic talent and can dribble at pace. He is a great player to watch and he will excite the fans.
“The defeat at Anfield was a major setback. But the team need to react well now.
“It’s still possible for us to fight in many competitions but that will depend on us.”