Fiorentina confirmed on Monday that Germany striker Mario Gomez will be out for up to seven weeks after damaging ligaments in his right knee in a 1-1 draw with Cagliari.
Former Bayern Munich striker Gomez was one of Vincenzo Montella's key summer signings but had to be stretchered off four minutes into the second half of Sunday's game after clashing with visiting goalkeeper Michael Agazzi.
Reports after the game said Gomez had suffered a "sprained knee with a partial lesion of the medial collateral ligament".
After scans on Monday Fiorentina said the striker had been diagnosed with "a grade two lesion on the medial collateral ligament of the knee".
The statement added that Gomez's recovery time would be in the region of "six to seven weeks".
The German will now be sidelined for key Serie A games as well as Fiorentina's group campaign in the Europa League, which begins Thursday at home against Pacos Ferreira.
He is also likely to miss Germany's final two qualifiers for the 2014 World Cup, with Joachim Loew's side yet to secure qualification for Brazil.
Fiorentina also confirmed Colombian midfielder Juan Cuadrado would be out for up to three weeks.
Cuadrado suffered a dislocated shoulder in a clash with Radja Nainggolan and had to be replaced.
In Italy's Serie A La Viola sit in third place, two points behind Napoli and on the same tally as second-placed Inter and Juventus, in fourth.