Levante will take their appeal against Copa del Rey elimination to the Court of Arbitration for Sport (CAS) after their initial move was rejected.
The LaLiga club alleged Barcelona used an ineligible player in the first leg of the last-16 tie, but their appeal was rejected by the Royal Spanish Football Federation (RFEF).
Levante beat Barca 2-1 at home in the first part of their two-legged clash, as Ernesto Valverde shuffled his pack, giving games to fringe players and youngsters.
Among the unfamiliar names in the starting XI was defender Chumi, who Levante believed to have been suspended for the match after accumulating five yellow cards for Barca's 'B' team in the third tier.