Daniele Sciusco, 29, Italian has pleaded guilty over the violent incident before Liverpool’s Champions League game against Roma in which a Liverpool fan was left seriously injured.
He admitted violent disorder which happened ahead of the first leg semi-final game at Anfield.
Filippo Lombardi, 21, has pleaded not guilty to the same charge and another of inflicting grievous bodily harm.
He was remanded in custody for trial at Preston Crown Court in October.
Liverpool fan Sean Cox, 53, from Dunboyne, County Meath, Republic of Ireland, remains in a critical condition after being attacked on 24 April outside The Albert pub on Breck Road, Walton.