The Argentinian has been missing with a thigh injury since November but has returned to training and took part in a full session alongside his team-mates on Monday.
Barca boss Gerardo Martino would not be drawn on whether Messi will start, and Saturday's top-of-the-table Primera Division clash with Atletico Madrid may affect his decision.
He said: "Messi rehabbed well and has trained like the rest of the team. Maybe he lacks some playing time, but with Leo I don't think that will be a problem.
"Messi gives us all a boost of confidence. With him at our side, we all feel more secure."
Sergio Busquets is also in Martino's squad for Wedensday, but injured trio Xavi, Marc Bartra and Dani Alves remain out.