Deco is convinced Chelsea will be champions come next May, despite conceding that The Blues are playing well below par at present.
Sunday's 2-2 draw against Fulham was another jolt to The Blues' title challenge and Luiz Felipe Scolari's team find themselves three points behind leaders Liverpool going into the New Year.
However Deco maintains that Chelsea are in a good position to overhaul The Reds between now and the season's close.
"I know that we have not been 100 percent in the last few matches and we have missed some chances to be top of the table," Deco said.
"But the important time to be top is at the end of the season and I believe that this team will finish as champions."
Scolari has come in for criticism in the wake of The Blues' less than convincing form, particularly at home, but Deco is adamant in his support for the Brazilian.
"Scolari has not changed, he is still a strong man and is the same coach as he was at the start of the season when everyone was praising him," added Deco.
"It's a long season and it is a big test in England. But I believe we will be champions and show what a good team we are over the season."