Goals from Ousmane Dembele and Lionel Messi saw Ronald Koeman’s side move three points clear of Andrea Pirlo’s Juventus at the top of Group G after two matches played.
Dembele opened the scoring with a deflected effort, while former Chelsea striker Alvaro Morata had three goals disallowed.
But a clumsy challenge from Federico Bernardeschi on Ansu Fati allowed Messi to wrap up the points from the penalty spot.
The match had been billed the battle of the GOATs when the draw was made, with Ronaldo part of Juventus’ squad, however, the Portugal international didn’t feature as he remains in isolation after testing positive for Covid-19.
And after seeing his side lose, he was cheekily mocked by Barcelona’s Twitter account.
‘We are glad you were about to see the GOAT on your pitch,’ wrote Barcelona.
Juventus quickly fired back: ‘You probably looked it up in the wrong dictionary. We’ll bring you the right one at Camp Nou.’
The sides will next meet in December in the final match of the group stages where, in truth, it would be a surprise if both weren’t already through to the last-16 after group rivals Dynamo Kiev and Ferencvaros drew 1-1.
Ronaldo was clearly frustrated to miss the tie as he had another positive coronavirus test, despite being symptomless.
He uploaded a photo to Instagram a few hours before the match with Barca, writing: ‘Feeling good and healthy! Forza Juve!’
A few minutes later he then commented on the photo, adding: ‘PCR is bullsh*t!’