The Uruguayan legend was suspended for kicking Honduran player Andy Najar but his one-match ban suspension was not upturned.
Mascherano revealed the league acted swiftly in rejecting the appeal, leaving Miami without their star forward for the semifinal-clinching clash.
“The player appealed the sanction because in this case, we were told the club couldn’t do it," Mascherano said.
"He appealed using the club’s resources, but within a few hours, the request was denied.
“We know it’s going to be a heated game, where there will be a war.
"We’ll try to implement our style, but also fight and win every duel because games are also decided there.”
