They got off to the best possible start after 22 minutes when Adriano converted from close range, but Mario Bermejes levelled moments later.
Meanwhile, it got worse for Celta mid-way through the second period when Jordi Alba made it three.
Read how it all unfolded in Sports Mole's minute-by-minute live commentary below.
Barcelona: Valdes; Alba, Busquets, Mascherano, Adriano; Iniesta, Xavi, Fabregas; Messi, Villa, Pedro
Celta Vigo: Varas; Mallo, Lago, Arceo, Oubina; Vila, Lopez, Fernandez; Aspas, Bermejo, Krohn-Dehli