Catania will be without defender Nicolas Spolli for a month and teammate Ciro Capuano for at least two weeks.
Both players limped off during Sunday night's 0-0 draw with Fiorentina.
Tests have now shown that Spolli, who fell awkwardly in a collision with Alberto Gilardino, has sprained his left knee with collateral ligament damage.
The Argentine is going to be out of action for around a month.
Capuano also went off the field and has been diagnosed with muscular trauma in his thigh, which is expected to keep him on the treatment table for 15 days.