Galliani knows Milan fans have concern after their disappointing 1-1 draw with Lecce.
"We must go on with tranquility. Now we will recover some injured players, and then if we can we may have to make some touch-ups," Galliani told the club's official website.
"Cassano arrived in January and he is an extraordinary player.
"We are living through a moment in which we are not 100 per cent, but we are first in the league, four points ahead. The others need to catch up, but we cannot make any mistakes."