The Oribici captain's career is in limbo after a clash with Gasperini last week. There are reports the halftime bust-up against Champions League opponents FC Midtjylland became physical.
“If Gomez did so well at Atalanta and in the national team, he owes it to only one person, Gasperini," Cassano told Bobo TV.
“He was a good player before, but if he did what he did, it's thanks to the coach. On the other hand, what Gasperini has created is thanks to Gasperini."
Cassano also commented on Gomez's social media where he stated people would "know the truth when I leave".
“If I have a problem, I tell the others what I think, I don't post it," he said. “In addition, Gasperini had already announced that he would change something because Atalanta conceded too many goals.
“And with the inclusion of [Matteo] Pessina, La Dea conceded less. Gomez must thank Gasperini, apologise and step aside.
“Gasp made a choice and rightly wants to have credibility with the other players in the locker room."