The Blaugrana are still picking the bones out of a disappointing domestic campaign which saw them surrender the Liga title to arch-rivals Real Madrid.
Inconsistency has been an issue for the Camp Nou giants, with Messi taking to airing his frustration in public.
The Argentine has suggested that Barca will struggle to mount a serious challenge for a European crown in their current state.
The mere presence of the mercurial Argentine does, however, give the Catalan giants a fighting chance every time they take to the field.
Messi has collected another Pichichi Trophy in 2019-20, having topped the Liga scoring charts with 25 goals, and remains a talismanic figure for Quique Setien’s side.
Barca are due to take in the second leg of a Champions League last-16 encounter with Napoli on Saturday, with that tie locked at 1-1, and Sylvinho believes they remain serious contender for the ultimate prize.
The former Blaugrana full-back told The Guardian: “Even a little bit of Messi is mucho Messi.
“He’s still the best. He can change a game in the seconds. He gets the ball, bluh, bluh, bluh, bluh, goal! A team with a player like that, look out, maybe they can win it.”
Ex-Brazil international Sylvinho found himself on the books at Camp Nou as Messi was making a senior breakthrough.
He admits that he could never have predicted how good the South American would become, with a standing among the all-time greats having been safely secured for some time now.
“He was the same then as now in many ways,” added Sylvinho.
“He didn't speak much, he was relaxed, he would just train and go home. He has a great family behind him.
“We didn't know how far he would go. We knew there was a lot of potential there. We knew he was something different, very different. But it's a lie to say we thought: this guy will win six Ballon d'Or prizes, you never know what will happen.”
Messi has previously played a part in four Champions League triumphs for Barcelona, but the last of those came back in 2015 and a global superpower is keen to return to the top of a continental game.