The Viola had hoped to have the former Bayern Munich striker available for Sunday's Serie A match against Bologna.
The Germany international has been sidelined since undergoing left knee surgery in mid-September and his comeback has been further postponed with the player struggling with inflammation to his knee.
"He (Gomez) is not expected to return to action soon, because first we must help Gomez work without feeling pain," Fiorentina doctor Paolo Manetti said.
"Only then will he return to training with the squad and then it will be down to coach Vincenzo Montella to decide when to play him.
"We are close to the complete solution of the problem, but it is first important to wait for the full recovery of this inflamed tendon."
The Viola go into this weekend's match on the back of Thursday's 2-1 triumph over Dnipro that allowed Montella's side to secure top spot in Europa League Group E.
The outcome allowed the Viola to bounce back from last weekend's 2-1 defeat at Roma that dropped Fiorentina to fifth position.
"We wanted to finish top of our group and we did it," Montella said. "I'm very happy especially considering we went into the match having lost a game at Roma that we didn't deserve to lose."
Rivals Bologna have not won since October 30.
The Rossoblu have collected three points since then - all from draws.
Last weekend's 2-1 loss at home to Juventus was their sixth defeat of the campaign and dropped Stefano Pioli's side to 19th position, two places and two points adrift of safety.
"I am confident we will come out of this difficult situation," Bologna defender Gyorgy Garics said.
"We are working hard to try to improve as a team."
Giuseppe Rossi, who is Serie A's top scorer with 12 goals netted this season, will lead Fiorentina's attack alongside Juan Guillermo Cuadrado.