Messi missed the first Clasico of the season with an elbow injury, but that did not stop Barca from beating Madrid 5-1.
A chill ran through Barcelona's supporters during the Spanish La Liga match with Valencia on Saturday when Messi sat down on the sideline, his right leg stretched before him, and receiving treatment from a team trainer. We need to use all the players we can and we'll analyse if we need to make changes tomorrow or Sunday.
I imagine it's nothing, but we'll wait a few hours.More news: Potential Liverpool Line-Up Versus West Ham As Fan Favourite Returns
Ousmane Dembele is close to recovering from an ankle injury.
Madrid were in disarray after the last meeting between these two Spanish giants as Barca moved back to the top of the table, seven points clear of ninth placed Madrid.
Whether it's a sign of defiance or just tempting fate, manager Santiago Solari says he hopes Messi is fit for the first leg.More news: Cancer awareness event to show benefits of exercise after diagnosis
He refuted the claim, though, that Messi's presence would have a major impact on the game.
Asked at the prematch news conference in Madrid whether he wanted his fellow Argentine to be available for Wednesday's game, Solari said it would be best for the spectacle for Messi to feature.
Both teams had enjoyed remarkable comebacks during the week to reach the Copa del Rey semifinals, with Barca thrashing Sevilla 6-1 to win 8-3 on aggregate and Valencia seeing off Getafe 3-1 for a 3-2 aggregate win with two goals in stoppage time.
"We put in a massive effort, it's not easy to play against Valencia who were feeling more confident after their recent results". Although the statistic is quite staggering, Ernesto Valverde, will be wary of what the over dependency on one man can cost as we progress to the end of the season.More news: Man Charged After Brisbane Airport Scare