Former Barcelona full-back Juliano Belletti insists Luis Enrique's men are "not invincible" and can be knocked out of the Champions League by Arsenal.
The Liga leaders arrive in London for Tuesday's last-16 first leg on the back of a 32-game unbeaten run and with fearsome forward trio Lionel Messi, Luis Suarez and Neymar in wonderful form.
They are overwhelming favourites to see off the Gunners - as they did in 2010 and 2011, as well as the 2006 final - but Belletti, who has experience of playing in England with Chelsea, cites football's unpredictability as one reason Arsenal can be optimistic.
"Barcelona are not invincible. That's one of the great things in football. You can have a respected team with a lot of quality, but that doesn't make it invincible," the Brazilian told Omnisport.
"Arsenal are currently at the best level for many years and their confidence gives them a chance. They have already proved their quality. But then comes the hardest part: trying to prevent Barcelona from showing their best qualities. That's really hard, especially with Barca's attack.
"But it has happened before. This Barcelona team have lost and it can happen again. Football is the only collective sport in the world where the best team does not always win."
Despite talking up Arsenal's chances, Belletti, who scored the winner in the 2006 showpiece in Paris, admits Barca hold the edge, due largely to their array of attacking options.
He added: "With Barca's level, they're favourites for everything. In the decisive matches, their decisive players are showing up.
"Even when the trio [Messi, Suarez and Neymar] do not play together... if one of them is out, the other two decide things, if two are out, the other one decides things.
"That gives them confidence and makes Barca favourites."