The two giants of Spanish football will be keen to seize on the opportunity to land a psychological advantage ahead of the Liga title run-in, with both currently trailing surprise leaders Atletico Madrid.
Barca and Real have already met twice in the league this term - Barca coming out on top both times - and their most recent meeting was one of the most explosive El Clasico clashes in recent years.
With seven goals, three penalties and a red card, March's contest surpassed expectations in terms of drama, but both sides would presumably settle for a more straightforward affair at the Mestalla on Wednesday.
Since seeing off Real Madrid at the Santiago Bernabeu last month, Barca have crashed out of the UEFA Champions League thanks to defeat against Atletico, while also slipping to third in the table.
They were beaten 1-0 by Granada on Saturday and face an uphill task to retain their league crown - adding even more importance to this fixture.
Real, meanwhile, were able to shake off the defeat to Barca to move into the semi-finals of the Champions League and they remain on Atletico's heels thanks to dominant wins over Rayo Vallecano, Real Sociedad and Almeria in recent weeks.
Carlo Ancelotti was without star performer Cristiano Ronaldo for the latter two victories and, even if his thigh injury keeps him out again, the Real coach maintains that his squad has enough quality to secure a first Copa win since 2011.
The Italian explained to El Mundo: "Cristiano is always missed but the players aren't saying, 'Oh my God, what will we do without him?'
"They have shown confidence and they know how to win without him.
"It is also a very good opportunity for someone to take centre stage in a final."
If the likes of Angel Di Maria and Isco can help cover Ronaldo's potential absence, Real will keep their treble hopes alive in Ancelotti's debut season, while for Barca, the competition now represents their best chance of silverware this term.
Sitting four points off Atletico, the 26-time Copa winners could see another trophy chance slip away if they fail to avenge their final defeat to Real in 2011.
Barca captain Carles Puyol claims victory would offer a "solution" to their recent poor form and also leapt to the defence of under-fire coach Gerardo Martino.
"We're a team and we all accept the blame. It's always easier to attack one man (Martino) than 25 players," he said.
"If things go right or wrong, it's (down to) the team.
"We analyse things and try (to) find solutions. The solution in this case is Wednesday.
"It's an important title against our biggest rival. Hopefully we can bring some joy to our fans after two disappointing results."
In what will be the seventh Copa final between the sides, Ancelotti is able to welcome back Sergio Ramos (neck), although Marcelo (hamstring), like Ronaldo, is a doubt.
Barca skipper Puyol may be required to return from a series of knee problems sooner than anticipated due to the injuries being carried by defensive pair Gerard Pique (pelvis) and Marc Bartra (hamstring).
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