Levante have filed a complaint to the Spanish football federation (RFEF) stating that Barcelona fielded an ineligible player in their Copa del Rey last-16, first-leg match, the La Liga side said in a statement on Twitter on Friday.
If the RFEF rule against Barca, who deny breaking any rules, they would be thrown out of the Copa, which they have won for the last four years, with Levante taking their place in the quarter-finals.
The last-eight draw is due to take place at 1700 local time on Friday.
Levante say that Barca defender Juan 'Chumi' Brandariz was ineligible to play in the game on Jan. 10, which Levante won 2-1, as he was serving a suspension for Barca's B team, which he had earned in a Spanish third-tier game.
Barca, who have lifted the Copa del Rey a record 30 times, won the second leg on Thursday 3-0 to win the tie 4-2 on aggregate.
Barca spokesman Josep Vives said on Thursday that the club thought Chumi was eligible to play as they had seen a RFEF memo, which said suspensions incurred by players for a reserve team should be served in the division in which they usually play.
The biggest stumbling block to any complaint is that the deadline expired on Monday, though the RFEF has previously approved claims made by teams after a deadline has passed.
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