Milanetto and Genoa are charged with conspiring to fix a match against Lazio in May 2011, with the fixture forming part of the on-going Calcioscomesse investigation led by the Italian Football Federation (FIGC).
But Mattia Grassani insists the claims against Genoa and Milanetto are completely unfounded.
"A sentence for Milanetto would be something that could only happen in science fiction," he told Italian news agency ANSA.
Lazio midfielder Stefano Mauri has also been implicated in the alleged fixing of the Serie A clash, but could be given a reduced punishment amid reports of a plea bargain.
And Grassani believes such action would weaken the case against Genoa and Milanetto.
"If one of the two people necessary to commit fraud was not there, the situation with (Stefano) Mauri would greatly undermine the prosecution’s case," he added.
A number of players have recently received bans as long as four years as the FIGC steps up its crackdown on match-fixing.
Torino goalkeeper Jean-Francois Gillet had his 43-month ban upheld last week, following an appeal.
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