Sadio Mane opened the scoring just 15 minutes into the encounter when he slammed into the bottom corner from a neat pass from Adam Lallana.
Jordan Henderson made it 2-0 early in the second half, tucking a low pass from Divock Origi in off of Javier Mascherano.
Almost immediately afterwards, Origi added a third, sliding it through the legs of Claudio Bravo.
And Marko Grujic added to the misery for Barcelona, scoring his side’s fourth in the dying minutes.