"I wouldn't like to venture a definitive answer, but in these last few days, the injury has evolved well and we have a good sensation," interim coach Jordi Roura told a news conference.
"But we will wait and see what happens in training.
"We have won important games without him but it will be important to have him in the team," added Roura, standing in for Tito Vilanova who is recovering from cancer treatment.
The Argentine World Player of the Year sat out Saturday's 1-0 La Liga win at home to Levante and travelled with the squad for the semi-final first leg match.
"Messi is with the team and he is able to compete, although that's a decision for the coaching staff," sporting director Andoni Zubizarreta said on Barca's website.
"We will not forego having the best possible team on the pitch," added the former Barca and Spain goalkeeper.
Midfielder Xavi added: "He is vital for us and if he is in good form, it's an extra guarantee for the team."
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