The Germany international has been sidelined since September with a knee injury, and was left on the bench during his side's Coppa Italia semi-final win over Udinese.
Gomez, who left Bundesliga giants Bayern Munich in the off-season, could still play a major role as Fiorentina look to seal a place in Europe this campaign.
"Mario is training well. He's enthusiastic about playing, but he's still not physically in top condition," Montella told a news conference on Friday.
"Hopefully he'll be able to play a little part tomorrow, but we'll have to wait and see.
"This game's a game in and of itself. It's a whole different story to the match last year."
Fiorentina's 2-0 win over Udinese on Tuesday saw them book a place in the Coppa Italia final against Napoli.
"The team is a bit tired, but it will be essential to restore our physical and mental well-being," he said.
"It's going to be a difficult game though because Inter have some great players who can really damage us.
"Hernanes has come in and has improved them already. He's a strong player and brings an element of unpredictability.
"Of course, we're on a high after the cup win, but we can't be too euphoric. We want to play with confidence, but we can't be overconfident."
