The former Camp Nou midfielder was shocked by their exit from Europa but has backed them to restore success with the current crop of young stars
Gerardo Martino's men have not lived up to the lofty expectations that previous seasons have seen them aspire to, having suffered Champions League elimination at the last-eight stage, Copa del Rey final failure and a slip-up in La Liga which has allowed Real Madrid and Atletico Madrid to become title favourites.
Deco, who played at Camp Nou between 2004 and 2008, does not think that the Catalans are in crisis and stressed that toying with their possession-centric style would be ill-advised despite their struggles during big games this season.
"It is difficult to say from the outside what is going wrong at Barca," he told Marca. "People talk a lot but, to me, what's happened is a normal and natural process.
"Barca have won a lot in recent years, they have been at a very high level - they were the best team in history for many people. And so it is normal what they are experiencing now.
"The club should focus on rediscovering success slowly, keeping stars like Lionel Messi or Andres Iniesta who remain essential to the club.
"There is no need to change the style because of two bad results, though. Barca already have a defined style and any reconstruction has to work within their existing form, as Louis van Gaal, Frank Rijkaard then Pep Guardiola did.
"Their style is to hog the ball and they're the best in the world at that."
The ex-Portugal international did admit he was stunned that Barcelona exited the Champions League at the quarter-final stage in 2013-14, though he was less surprised that it was Atletico who dumped them out of the competition.
"I was shocked at their Champions League elimination," Deco continued. "For me they were one of the favourites this season.
"But I was not surprised by who knocked them out: Atletico. They are doing something special this season, that's the truth."
After defeating Barca in the quarter-final stage, Atletico knocked out Chelsea on Wednesday to set up a final meeting with Real Madrid.