Levante president Quico Catalan says the club will lodge a formal complaint against Barcelona with the Royal Spanish Football Federation (RFEF) for fielding an ineligible player in the two sides' Copa del Rey meeting last week.
Barcelona sources had earlier told ESPN FC that the club had not breached competition rules by selecting B team defender Juan "Chumi" Brandariz.
A report in El Mundo on Thursday claimed Barca were facing expulsion from the Spanish cup after picking Chumi in Valencia last Thursday when he should have been banned.
"Independent of the result [in the second leg] Levante will take the situation to the RFEF regarding Barcelona's possible ineligible lineup," Catalan told reporters.
"We understand there is a solid law that allows the club to bring this to the Federation."
Chumi had been booked the weekend before the game for the fifth time this season, earning an automatic one-match suspension.
That ban was subsequently served on Sunday as Barca B beat Alcoyano, but the El Mundo report says he should not have been available for first-team selection until he'd served his ban during a first-team game.
However, Barca sources told ESPN FC that the rules have recently changed. Bans of one and two games should be served in the competition in which they are accrued -- in this case that would cover La Liga or the Spanish third tier, where Barca B play.
Levante will argue that another rule suggests this is not the case when it comes to players switching between teams within one club.
However, a defiant Ernesto Valverde said the Blaugrana have done nothing wrong.
"There were never any doubts about [playing] Chumi, none. We did everything right. [On Friday], we will be in the draw for the quarterfinal," Valverde said after Barcelona's 3-0 win in the second leg on Thursday.
"We have no doubts, not before, not during and not now. We have the security of knowing we did everything right. We knew that Chumi was banned and not available for [the La Liga] game against Eibar, but he could play in the cup.
"We're convinced we acted correctly. Absolutely. We've won where we had to win to progress: on the pitch."
A complaint should have been filed by Levante or another club within 48 hours of the infraction occurring. That period has since passed but the RFEF could still decide to look into the issue.
The RFEF have not yet made an official comment on the situation.
The case draws parallels with Real Madrid, who were kicked out of the competition for fielding Denis Cheryshev against Cadiz in 2015.
Russia international Cheryshev was supposed to carry over a suspension from his loan spell with Villarreal the previous season.
Levante beat a Barca side which included Chumi 2-1 last Thursday. The two sides meet in the second leg of their last-16 tie on Thursday at Camp Nou.