Messi fit to face Porto: Inter Miami's Mascherano
A video emerged of Messi touching his left leg during the session on Wednesday, but Mascherano confirmed the veteran forward was ready for Miami's second Group A match in Atlanta.
"On the trip from Miami to Atlanta I saw that came out in some places, but Leo is fit, he trained, he completed the whole session," Mascherano told reporters.
"He was touching his leg, sometimes people touch themselves, but there's no problem, he's fit and obviously he will play tomorrow."
The coach said Messi's former Barcelona team-mate Jordi Alba was available after missing the opening 0-0 draw against Al Ahly due to injury.
"We'll evaluate what's best for us, if he starts or not," said the coach. "Actually, I already know but I won't tell you."
Mascherano meanwhile said retaining possession would be the key against Portugal's Porto, regular Champions League participants who are likely to provide the MLS team with a stern test.
"We have players who feel much more comfortable when they're in possession, dominating, and having control of the game through the ball," said the Argentine.
"Of course, we're facing a team that also is used to doing that, who are a high level side.
"But on the pitch we're 11 against 11, we'll try to shut down their strengths, expose their weaknesses and try to have a great game to get a good result."
Inter Miami midfielder Sergio Busquets, a member of Spain's 2010 World Cup-winning side and one of Messi's former Barcelona team-mates, admitted his team would be up against it at the Mercedes-Benz stadium.
"They have very good players, they have reinforced and we know that it will be very difficult," Busquets told reporters.
"They are a team that compete every year for their league, against other great teams like Sporting and Benfica.
"We will try to be as solid as possible, stick close together and try to do the best we can as a team.
"If we get chances, we have the individuals (who can finish them), but above all we have to be solid and keep a clean sheet."