The 36-year-old has said that the Brazil ace has a long way to go before his name can be mentioned in the same breath as the superstar duo
The 21-year-old attacker has yet to scale the heights expected of him as he continues to adapt to life in la Liga following his €57 million move from Santos in the summer, having netted just three times in 10 appearances so far this season.
But while acknowledging that Neymar has the ability to establish himself as one of the world's finest, Deco believes the youngster has a long road ahead of him.
"He has potential for it, for sure," the former Brazil and Blaugrana midfielder told El Mundo Deportivo. "But this is a long way away.
"Comparisons with Messi or Cristiano are easy because they have matured, but football is not only about quality - you also have to mature."
Deco, who called time on his illustrious playing career in August, before being handed a one-year ban from the game for doping, went on to plead his innocence in the case.
"Fluminense do not have a great medical structure, unlike Barcelona or Chelsea," the 36-year-old explained.
"That's why I got my own nutritionist and he sent my vitamins to a pharmacy for them to include vitamin supplements.
"These pharmacies also make medicine and my vitamins were accidentally contaminated. The contamination was small, but it led to a positive test for two banned substances.
"One is used as a diuretic and another is used to treat breast cancer, but contains anabolic steroids, which are useless in football.
"It annoys me, but deep down I do not care because I am already retired, unlike those who are still active.
"If this happens to a 25-year-old boy then his career could be over."